diff --git a/__tests__/changedFiles.test.ts b/__tests__/changedFiles.test.ts
index 0f611c5b9..cbcebb4d3 100644
--- a/__tests__/changedFiles.test.ts
+++ b/__tests__/changedFiles.test.ts
@@ -4,12 +4,16 @@ import {
   checkAnyChangedFiles,
   toChangedFilesMatchConfig
 } from '../src/changedFiles';
+import {PrFileType} from '../src/labeler';
 
 jest.mock('@actions/core');
 jest.mock('@actions/github');
 
 describe('checkAllChangedFiles', () => {
-  const changedFiles = ['foo.txt', 'bar.txt'];
+  const changedFiles: PrFileType[] = [
+    {name: 'foo.txt', size: 6},
+    {name: 'bar.txt', size: 20}
+  ];
 
   describe('when the globs match every file that has been changed', () => {
     const globs = ['*.txt'];
@@ -31,7 +35,10 @@ describe('checkAllChangedFiles', () => {
 });
 
 describe('checkAnyChangedFiles', () => {
-  const changedFiles = ['foo.txt', 'bar.txt'];
+  const changedFiles: PrFileType[] = [
+    {name: 'foo.txt', size: 6},
+    {name: 'bar.txt', size: 20}
+  ];
 
   describe('when any glob matches any of the files that have changed', () => {
     const globs = ['*.txt', '*.md'];
diff --git a/__tests__/fixtures/all_options.yml b/__tests__/fixtures/all_options.yml
index f4d5ecc5f..ce0d4fed6 100644
--- a/__tests__/fixtures/all_options.yml
+++ b/__tests__/fixtures/all_options.yml
@@ -1,14 +1,24 @@
-label1:
-  - any:
-      - changed-files: ['glob']
-      - head-branch: ['regexp']
-      - base-branch: ['regexp']
-  - all:
-      - changed-files: ['glob']
-      - head-branch: ['regexp']
-      - base-branch: ['regexp']
+label-config:
+  label1:
+    - any:
+        - changed-files: ['glob']
+        - head-branch: ['regexp']
+        - base-branch: ['regexp']
+    - all:
+        - changed-files: ['glob']
+        - head-branch: ['regexp']
+        - base-branch: ['regexp']
 
-label2:
-  - changed-files: ['glob']
-  - head-branch: ['regexp']
-  - base-branch: ['regexp']
+  label2:
+    - changed-files: ['glob']
+    - head-branch: ['regexp']
+    - base-branch: ['regexp']
+size-config: >
+  {
+    "100": "XS",
+    "200": "S",
+    "500": "M",
+    "800": "L",
+    "1000": "XL",
+    "2000": "XXL"
+  }
diff --git a/__tests__/fixtures/any_and_all.yml b/__tests__/fixtures/any_and_all.yml
index 5b8901e5b..4abe8cc95 100644
--- a/__tests__/fixtures/any_and_all.yml
+++ b/__tests__/fixtures/any_and_all.yml
@@ -1,6 +1,7 @@
-tests:
-  - any:
-      - head-branch: ['^tests/', '^test/']
-      - changed-files: ['tests/**/*']
-  - all:
-      - changed-files: ['!tests/requirements.txt']
+label-config:
+  tests:
+    - any:
+        - head-branch: ['^tests/', '^test/']
+        - changed-files: ['tests/**/*']
+    - all:
+        - changed-files: ['!tests/requirements.txt']
diff --git a/__tests__/fixtures/branches.yml b/__tests__/fixtures/branches.yml
index 1ad12ac6f..8484d3136 100644
--- a/__tests__/fixtures/branches.yml
+++ b/__tests__/fixtures/branches.yml
@@ -1,11 +1,12 @@
-test-branch:
-  - head-branch: '^test/'
+label-config:
+  test-branch:
+    - head-branch: '^test/'
 
-feature-branch:
-  - head-branch: '/feature/'
+  feature-branch:
+    - head-branch: '/feature/'
 
-bug-branch:
-  - head-branch: '^bug/|fix/'
+  bug-branch:
+    - head-branch: '^bug/|fix/'
 
-array-branch:
-  - head-branch: ['^array/']
+  array-branch:
+    - head-branch: ['^array/']
diff --git a/__tests__/fixtures/no_size_config.yml b/__tests__/fixtures/no_size_config.yml
new file mode 100644
index 000000000..fc413be70
--- /dev/null
+++ b/__tests__/fixtures/no_size_config.yml
@@ -0,0 +1,15 @@
+label-config:
+  label1:
+    - any:
+        - changed-files: ['glob']
+        - head-branch: ['regexp']
+        - base-branch: ['regexp']
+    - all:
+        - changed-files: ['glob']
+        - head-branch: ['regexp']
+        - base-branch: ['regexp']
+
+  label2:
+    - changed-files: ['glob']
+    - head-branch: ['regexp']
+    - base-branch: ['regexp']
diff --git a/__tests__/fixtures/not_supported.yml b/__tests__/fixtures/not_supported.yml
index 8af7523ae..5ac43e684 100644
--- a/__tests__/fixtures/not_supported.yml
+++ b/__tests__/fixtures/not_supported.yml
@@ -1,3 +1,4 @@
-label:
-  - all:
-      - unknown: 'this-is-not-supported'
+label-config:
+  label:
+    - all:
+        - unknown: 'this-is-not-supported'
diff --git a/__tests__/fixtures/only_pdfs.yml b/__tests__/fixtures/only_pdfs.yml
index a645acfc6..301587871 100644
--- a/__tests__/fixtures/only_pdfs.yml
+++ b/__tests__/fixtures/only_pdfs.yml
@@ -1,2 +1,3 @@
-touched-a-pdf-file:
-  - changed-files: ['*.pdf']
+label-config:
+  touched-a-pdf-file:
+    - changed-files: ['*.pdf']
diff --git a/__tests__/fixtures/only_pdfs_custom_size.yml b/__tests__/fixtures/only_pdfs_custom_size.yml
new file mode 100644
index 000000000..e7565b77a
--- /dev/null
+++ b/__tests__/fixtures/only_pdfs_custom_size.yml
@@ -0,0 +1,12 @@
+label-config:
+  touched-a-pdf-file:
+    - changed-files: ['*.pdf']
+size-config: >
+  {
+    "100": "XS",
+    "200": "S",
+    "500": "M",
+    "800": "L",
+    "1000": "XL",
+    "2000": "XXL"
+  }
diff --git a/__tests__/labeler.test.ts b/__tests__/labeler.test.ts
index 0b9fb307b..62b0f779f 100644
--- a/__tests__/labeler.test.ts
+++ b/__tests__/labeler.test.ts
@@ -1,9 +1,12 @@
 import {
   checkMatchConfigs,
+  checkSizeConfigs,
   MatchConfig,
   toMatchConfig,
   getLabelConfigMapFromObject,
-  BaseMatchConfig
+  getSizeConfigMapFromObject,
+  BaseMatchConfig,
+  PrFileType
 } from '../src/labeler';
 import * as yaml from 'js-yaml';
 import * as core from '@actions/core';
@@ -58,6 +61,40 @@ describe('getLabelConfigMapFromObject', () => {
   });
 });
 
+describe('getSizeConfigMapFromObject', () => {
+  describe('get default sizes when size-config is present', () => {
+    const yamlObject = loadYaml('__tests__/fixtures/no_size_config.yml');
+    const expected = new Map<number, string>();
+    expected.set(0, 'XS');
+    expected.set(10, 'S');
+    expected.set(30, 'M');
+    expected.set(100, 'L');
+    expected.set(500, 'XL');
+    expected.set(1000, 'XXL');
+
+    it('returns a SizeConfig', () => {
+      const result = getSizeConfigMapFromObject(yamlObject);
+      expect(result).toEqual(expected);
+    });
+  });
+
+  describe('get configured sizes when size-config is present', () => {
+    const yamlObject = loadYaml('__tests__/fixtures/all_options.yml');
+    const expected = new Map<number, string>();
+    expected.set(100, 'XS');
+    expected.set(200, 'S');
+    expected.set(500, 'M');
+    expected.set(800, 'L');
+    expected.set(1000, 'XL');
+    expected.set(2000, 'XXL');
+
+    it('returns a SizeConfig', () => {
+      const result = getSizeConfigMapFromObject(yamlObject);
+      expect(result).toEqual(expected);
+    });
+  });
+});
+
 describe('toMatchConfig', () => {
   describe('when all expected config options are present', () => {
     const config = {
@@ -92,14 +129,17 @@ describe('checkMatchConfigs', () => {
     const matchConfig: MatchConfig[] = [{any: [{changedFiles: ['*.txt']}]}];
 
     it('returns true when our pattern does match changed files', () => {
-      const changedFiles = ['foo.txt', 'bar.txt'];
+      const changedFiles: PrFileType[] = [
+        {name: 'foo.txt', size: 6},
+        {name: 'bar.txt', size: 20}
+      ];
       const result = checkMatchConfigs(changedFiles, matchConfig);
 
       expect(result).toBeTruthy();
     });
 
     it('returns false when our pattern does not match changed files', () => {
-      const changedFiles = ['foo.docx'];
+      const changedFiles: PrFileType[] = [{name: 'foo.docx', size: 13}];
       const result = checkMatchConfigs(changedFiles, matchConfig);
 
       expect(result).toBeFalsy();
@@ -109,7 +149,10 @@ describe('checkMatchConfigs', () => {
       const matchConfig: MatchConfig[] = [
         {any: [{changedFiles: ['*.txt']}, {headBranch: ['some-branch']}]}
       ];
-      const changedFiles = ['foo.txt', 'bar.txt'];
+      const changedFiles: PrFileType[] = [
+        {name: 'foo.txt', size: 6},
+        {name: 'bar.txt', size: 20}
+      ];
 
       const result = checkMatchConfigs(changedFiles, matchConfig);
       expect(result).toBe(true);
@@ -121,7 +164,10 @@ describe('checkMatchConfigs', () => {
       {any: [{changedFiles: ['*.txt']}]},
       {any: [{headBranch: ['some-branch']}]}
     ];
-    const changedFiles = ['foo.txt', 'bar.md'];
+    const changedFiles: PrFileType[] = [
+      {name: 'foo.txt', size: 6},
+      {name: 'bar.md', size: 20}
+    ];
 
     it('returns false when only one config matches', () => {
       const result = checkMatchConfigs(changedFiles, matchConfig);
@@ -138,3 +184,92 @@ describe('checkMatchConfigs', () => {
     });
   });
 });
+
+describe('checkSizeConfigs', () => {
+  describe('when a single size config is provided', () => {
+    const sizeConfig: Map<number, string> = new Map<number, string>();
+    sizeConfig.set(100, 'XS');
+    sizeConfig.set(200, 'S');
+    sizeConfig.set(500, 'M');
+    sizeConfig.set(800, 'L');
+    sizeConfig.set(1000, 'XL');
+    sizeConfig.set(2000, 'XXL');
+
+    it('returns size/XXS when the size is less than the smallest size', () => {
+      const changedFiles: PrFileType[] = [
+        {name: 'foo.txt', size: 10},
+        {name: 'baz.txt', size: 10},
+        {name: 'bar.txt', size: 10}
+      ];
+      const result = checkSizeConfigs(changedFiles, sizeConfig);
+
+      expect(result).toBe('size/XXS');
+    });
+
+    it('returns size/XS when the size is less than the smallest size', () => {
+      const changedFiles: PrFileType[] = [
+        {name: 'foo.txt', size: 50},
+        {name: 'baz.txt', size: 50},
+        {name: 'bar.txt', size: 50}
+      ];
+      const result = checkSizeConfigs(changedFiles, sizeConfig);
+
+      expect(result).toBe('size/XS');
+    });
+
+    it('returns size/S when the size is less than the smallest size', () => {
+      const changedFiles: PrFileType[] = [
+        {name: 'foo.txt', size: 100},
+        {name: 'baz.txt', size: 100},
+        {name: 'bar.txt', size: 100}
+      ];
+      const result = checkSizeConfigs(changedFiles, sizeConfig);
+
+      expect(result).toBe('size/S');
+    });
+
+    it('returns size/M when the size is less than the smallest size', () => {
+      const changedFiles: PrFileType[] = [
+        {name: 'foo.txt', size: 200},
+        {name: 'baz.txt', size: 200},
+        {name: 'bar.txt', size: 200}
+      ];
+      const result = checkSizeConfigs(changedFiles, sizeConfig);
+
+      expect(result).toBe('size/M');
+    });
+
+    it('returns size/L when the size is less than the smallest size', () => {
+      const changedFiles: PrFileType[] = [
+        {name: 'foo.txt', size: 300},
+        {name: 'baz.txt', size: 300},
+        {name: 'bar.txt', size: 300}
+      ];
+      const result = checkSizeConfigs(changedFiles, sizeConfig);
+
+      expect(result).toBe('size/L');
+    });
+
+    it('returns size/XL when the size is less than the smallest size', () => {
+      const changedFiles: PrFileType[] = [
+        {name: 'foo.txt', size: 400},
+        {name: 'baz.txt', size: 400},
+        {name: 'bar.txt', size: 400}
+      ];
+      const result = checkSizeConfigs(changedFiles, sizeConfig);
+
+      expect(result).toBe('size/XL');
+    });
+
+    it('returns size/XXL when the size is less than the smallest size', () => {
+      const changedFiles: PrFileType[] = [
+        {name: 'foo.txt', size: 700},
+        {name: 'baz.txt', size: 700},
+        {name: 'bar.txt', size: 700}
+      ];
+      const result = checkSizeConfigs(changedFiles, sizeConfig);
+
+      expect(result).toBe('size/XXL');
+    });
+  });
+});
diff --git a/__tests__/main.test.ts b/__tests__/main.test.ts
index 4dfe51120..b234674ed 100644
--- a/__tests__/main.test.ts
+++ b/__tests__/main.test.ts
@@ -1,4 +1,4 @@
-import {run} from '../src/labeler';
+import {run, PrFileType} from '../src/labeler';
 import * as github from '@actions/github';
 import * as core from '@actions/core';
 
@@ -7,6 +7,13 @@ const fs = jest.requireActual('fs');
 jest.mock('@actions/core');
 jest.mock('@actions/github');
 
+type mockGitHubResponseChangedFilesType = {
+  filename: string;
+  additions: number;
+  deletions: number;
+  changes: number;
+};
+
 const gh = github.getOctokit('_');
 const addLabelsMock = jest.spyOn(gh.rest.issues, 'addLabels');
 const removeLabelMock = jest.spyOn(gh.rest.issues, 'removeLabel');
@@ -17,6 +24,9 @@ const getPullMock = jest.spyOn(gh.rest.pulls, 'get');
 const yamlFixtures = {
   'branches.yml': fs.readFileSync('__tests__/fixtures/branches.yml'),
   'only_pdfs.yml': fs.readFileSync('__tests__/fixtures/only_pdfs.yml'),
+  'only_pdfs_custom_size.yml': fs.readFileSync(
+    '__tests__/fixtures/only_pdfs_custom_size.yml'
+  ),
   'not_supported.yml': fs.readFileSync('__tests__/fixtures/not_supported.yml'),
   'any_and_all.yml': fs.readFileSync('__tests__/fixtures/any_and_all.yml')
 };
@@ -26,7 +36,12 @@ afterAll(() => jest.restoreAllMocks());
 describe('run', () => {
   it('adds labels to PRs that match our glob patterns', async () => {
     usingLabelerConfigYaml('only_pdfs.yml');
-    mockGitHubResponseChangedFiles('foo.pdf');
+    mockGitHubResponseChangedFiles({
+      filename: 'foo.pdf',
+      additions: 10,
+      deletions: 10,
+      changes: 10
+    });
 
     await run();
 
@@ -42,7 +57,12 @@ describe('run', () => {
 
   it('does not add labels to PRs that do not match our glob patterns', async () => {
     usingLabelerConfigYaml('only_pdfs.yml');
-    mockGitHubResponseChangedFiles('foo.txt');
+    mockGitHubResponseChangedFiles({
+      filename: 'foo.txt',
+      additions: 10,
+      deletions: 10,
+      changes: 10
+    });
 
     await run();
 
@@ -75,7 +95,12 @@ describe('run', () => {
       );
 
     usingLabelerConfigYaml('only_pdfs.yml');
-    mockGitHubResponseChangedFiles('foo.txt');
+    mockGitHubResponseChangedFiles({
+      filename: 'foo.txt',
+      additions: 10,
+      deletions: 10,
+      changes: 10
+    });
     getPullMock.mockResolvedValue(<any>{
       data: {
         labels: [{name: 'touched-a-pdf-file'}]
@@ -111,7 +136,12 @@ describe('run', () => {
       );
 
     usingLabelerConfigYaml('only_pdfs.yml');
-    mockGitHubResponseChangedFiles('foo.txt');
+    mockGitHubResponseChangedFiles({
+      filename: 'foo.txt',
+      additions: 10,
+      deletions: 10,
+      changes: 10
+    });
     getPullMock.mockResolvedValue(<any>{
       data: {
         labels: [{name: 'touched-a-pdf-file'}]
@@ -184,7 +214,12 @@ describe('run', () => {
 
   it('adds a label when matching any and all patterns are provided', async () => {
     usingLabelerConfigYaml('any_and_all.yml');
-    mockGitHubResponseChangedFiles('tests/test.ts');
+    mockGitHubResponseChangedFiles({
+      filename: 'tests/test.ts',
+      additions: 10,
+      deletions: 10,
+      changes: 10
+    });
     await run();
 
     expect(addLabelsMock).toHaveBeenCalledTimes(1);
@@ -198,12 +233,143 @@ describe('run', () => {
 
   it('does not add a label when not all any and all patterns are matched', async () => {
     usingLabelerConfigYaml('any_and_all.yml');
-    mockGitHubResponseChangedFiles('tests/requirements.txt');
+    mockGitHubResponseChangedFiles({
+      filename: 'tests/requirements.txt',
+      additions: 10,
+      deletions: 10,
+      changes: 10
+    });
     await run();
 
     expect(addLabelsMock).toHaveBeenCalledTimes(0);
     expect(removeLabelMock).toHaveBeenCalledTimes(0);
   });
+
+  it('(with check-size: true, sync-labels: true) it deletes preexisting PR labels that no longer match the glob pattern and adds the size label', async () => {
+    const mockInput = {
+      'repo-token': 'foo',
+      'configuration-path': 'bar',
+      'check-size': 'true',
+      'sync-labels': 'true'
+    };
+
+    jest
+      .spyOn(core, 'getInput')
+      .mockImplementation((name: string, ...opts) => mockInput[name]);
+    jest
+      .spyOn(core, 'getBooleanInput')
+      .mockImplementation(
+        (name: string, ...opts) => mockInput[name] === 'true'
+      );
+
+    usingLabelerConfigYaml('only_pdfs.yml');
+    mockGitHubResponseChangedFiles({
+      filename: 'foo.txt',
+      additions: 10,
+      deletions: 10,
+      changes: 10
+    });
+    getPullMock.mockResolvedValue(<any>{
+      data: {
+        labels: [{name: 'touched-a-pdf-file'}]
+      }
+    });
+
+    await run();
+
+    expect(addLabelsMock).toHaveBeenCalledTimes(1);
+    expect(addLabelsMock).toHaveBeenCalledWith({
+      owner: 'monalisa',
+      repo: 'helloworld',
+      issue_number: 123,
+      labels: ['size/M']
+    });
+    expect(removeLabelMock).toHaveBeenCalledTimes(1);
+    expect(removeLabelMock).toHaveBeenCalledWith({
+      owner: 'monalisa',
+      repo: 'helloworld',
+      issue_number: 123,
+      name: 'touched-a-pdf-file'
+    });
+  });
+
+  it('(with check-size: true) adds a label based on the PR size', async () => {
+    const mockInput = {
+      'repo-token': 'foo',
+      'configuration-path': 'bar',
+      'check-size': 'true'
+    };
+
+    jest
+      .spyOn(core, 'getInput')
+      .mockImplementation((name: string, ...opts) => mockInput[name]);
+    jest
+      .spyOn(core, 'getBooleanInput')
+      .mockImplementation(
+        (name: string, ...opts) => mockInput[name] === 'true'
+      );
+
+    usingLabelerConfigYaml('only_pdfs.yml');
+    mockGitHubResponseChangedFiles({
+      filename: 'foo.txt',
+      additions: 10,
+      deletions: 10,
+      changes: 10
+    });
+    getPullMock.mockResolvedValue(<any>{
+      data: {
+        labels: [{name: 'touched-a-pdf-file'}]
+      }
+    });
+
+    await run();
+
+    expect(addLabelsMock).toHaveBeenCalledTimes(1);
+    expect(addLabelsMock).toHaveBeenCalledWith({
+      owner: 'monalisa',
+      repo: 'helloworld',
+      issue_number: 123,
+      labels: ['size/M']
+    });
+  });
+});
+
+it('(with check-size: true with custom size config) adds a label based on the PR size and customf size config', async () => {
+  const mockInput = {
+    'repo-token': 'foo',
+    'configuration-path': 'bar',
+    'check-size': 'true'
+  };
+
+  jest
+    .spyOn(core, 'getInput')
+    .mockImplementation((name: string, ...opts) => mockInput[name]);
+  jest
+    .spyOn(core, 'getBooleanInput')
+    .mockImplementation((name: string, ...opts) => mockInput[name] === 'true');
+
+  usingLabelerConfigYaml('only_pdfs_custom_size.yml');
+  mockGitHubResponseChangedFiles({
+    filename: 'foo.txt',
+    additions: 10,
+    deletions: 10,
+    changes: 10
+  });
+  getPullMock.mockResolvedValue(<any>{
+    data: {
+      labels: [{name: 'touched-a-pdf-file'}]
+    }
+  });
+
+  await run();
+
+  expect(addLabelsMock).toHaveBeenCalledTimes(1);
+  expect(addLabelsMock).toHaveBeenCalledWith({
+    owner: 'monalisa',
+    repo: 'helloworld',
+    issue_number: 123,
+    labels: ['size/XXS']
+  });
 });
 
 function usingLabelerConfigYaml(fixtureName: keyof typeof yamlFixtures): void {
@@ -212,7 +378,14 @@ function usingLabelerConfigYaml(fixtureName: keyof typeof yamlFixtures): void {
   });
 }
 
-function mockGitHubResponseChangedFiles(...files: string[]): void {
-  const returnValue = files.map(f => ({filename: f}));
+function mockGitHubResponseChangedFiles(
+  ...files: mockGitHubResponseChangedFilesType[]
+): void {
+  const returnValue = files.map(f => ({
+    filename: f.filename,
+    additions: f.additions,
+    deletions: f.deletions,
+    changes: f.changes
+  }));
   paginateMock.mockReturnValue(<any>returnValue);
 }
diff --git a/action.yml b/action.yml
index a3df342b6..1f6bd40f2 100644
--- a/action.yml
+++ b/action.yml
@@ -14,6 +14,10 @@ inputs:
     description: 'Whether or not to remove labels when matching files are reverted'
     default: false
     required: false
+  check-size:
+    description: 'Whether or not to apply labels based on PR size'
+    default: false
+    required: false
 
 runs:
   using: 'node16'
diff --git a/dist/index.js b/dist/index.js
index 71af26a98..4b59e4032 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -162,7 +162,12 @@ function getChangedFiles(client, prNumber) {
             pull_number: prNumber
         });
         const listFilesResponse = yield client.paginate(listFilesOptions);
-        const changedFiles = listFilesResponse.map((f) => f.filename);
+        const changedFiles = listFilesResponse.map((f) => {
+            return {
+                name: f.filename,
+                size: (f.additions + f.deletions + f.changes)
+            };
+        });
         core.debug('found changed files:');
         for (const file of changedFiles) {
             core.debug('  ' + file);
@@ -190,7 +195,7 @@ function isAnyMatch(changedFile, matchers) {
     core.debug(`    matching patterns against file ${changedFile}`);
     for (const matcher of matchers) {
         core.debug(`     - ${printPattern(matcher)}`);
-        if (matcher.match(changedFile)) {
+        if (matcher.match(changedFile.name)) {
             core.debug(`    ${printPattern(matcher)} matched`);
             return true;
         }
@@ -202,7 +207,7 @@ function isAllMatch(changedFile, matchers) {
     core.debug(`    matching patterns against file ${changedFile}`);
     for (const matcher of matchers) {
         core.debug(`     - ${printPattern(matcher)}`);
-        if (!matcher.match(changedFile)) {
+        if (!matcher.match(changedFile.name)) {
             core.debug(`    ${printPattern(matcher)} did not match`);
             return false;
         }
@@ -276,19 +281,28 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
     });
 };
 Object.defineProperty(exports, "__esModule", ({ value: true }));
-exports.checkAll = exports.checkAny = exports.checkMatchConfigs = exports.toMatchConfig = exports.getLabelConfigMapFromObject = exports.run = void 0;
+exports.checkAll = exports.checkAny = exports.checkSizeConfigs = exports.checkMatchConfigs = exports.toMatchConfig = exports.getSizeConfigMapFromObject = exports.getLabelConfigMapFromObject = exports.run = void 0;
 const core = __importStar(__nccwpck_require__(2186));
 const github = __importStar(__nccwpck_require__(5438));
 const yaml = __importStar(__nccwpck_require__(1917));
 const changedFiles_1 = __nccwpck_require__(7358);
 const branch_1 = __nccwpck_require__(8045);
 const ALLOWED_CONFIG_KEYS = ['changed-files', 'head-branch', 'base-branch'];
+const DEFAULT_SIZES = new Map([
+    [0, 'XS'],
+    [10, 'S'],
+    [30, 'M'],
+    [100, 'L'],
+    [500, 'XL'],
+    [1000, 'XXL']
+]);
 function run() {
     return __awaiter(this, void 0, void 0, function* () {
         try {
             const token = core.getInput('repo-token');
             const configPath = core.getInput('configuration-path', { required: true });
             const syncLabels = core.getBooleanInput('sync-labels');
+            const checkSizeEnabled = core.getBooleanInput('check-size');
             const prNumber = getPrNumber();
             if (!prNumber) {
                 core.info('Could not get pull request number from context, exiting');
@@ -302,10 +316,10 @@ function run() {
             });
             core.debug(`fetching changed files for pr #${prNumber}`);
             const changedFiles = yield (0, changedFiles_1.getChangedFiles)(client, prNumber);
-            const labelConfigs = yield getMatchConfigs(client, configPath);
+            const labelerConfigs = yield getConfigs(client, configPath);
             const labels = [];
             const labelsToRemove = [];
-            for (const [label, configs] of labelConfigs.entries()) {
+            for (const [label, configs] of labelerConfigs.labels.entries()) {
                 core.debug(`processing ${label}`);
                 if (checkMatchConfigs(changedFiles, configs)) {
                     labels.push(label);
@@ -314,6 +328,10 @@ function run() {
                     labelsToRemove.push(label);
                 }
             }
+            if (checkSizeEnabled) {
+                const sizeLabel = checkSizeConfigs(changedFiles, labelerConfigs.size);
+                labels.push(sizeLabel);
+            }
             if (labels.length > 0) {
                 yield addLabels(client, prNumber, labels);
             }
@@ -335,13 +353,16 @@ function getPrNumber() {
     }
     return pullRequest.number;
 }
-function getMatchConfigs(client, configurationPath) {
+function getConfigs(client, configurationPath) {
     return __awaiter(this, void 0, void 0, function* () {
         const configurationContent = yield fetchContent(client, configurationPath);
         // loads (hopefully) a `{[label:string]: MatchConfig[]}`, but is `any`:
         const configObject = yaml.load(configurationContent);
-        // transform `any` => `Map<string,MatchConfig[]>` or throw if yaml is malformed:
-        return getLabelConfigMapFromObject(configObject);
+        return {
+            // transform `any` => `Map<string,MatchConfig[]>` or throw if yaml is malformed:
+            labels: getLabelConfigMapFromObject(configObject),
+            size: getSizeConfigMapFromObject(configObject)
+        };
     });
 }
 function fetchContent(client, repoPath) {
@@ -356,9 +377,10 @@ function fetchContent(client, repoPath) {
     });
 }
 function getLabelConfigMapFromObject(configObject) {
+    const labelConfigObject = configObject['label-config'];
     const labelMap = new Map();
-    for (const label in configObject) {
-        const configOptions = configObject[label];
+    for (const label in labelConfigObject) {
+        const configOptions = labelConfigObject[label];
         if (!Array.isArray(configOptions) ||
             !configOptions.every(opts => typeof opts === 'object')) {
             throw Error(`found unexpected type for label '${label}' (should be array of config options)`);
@@ -403,6 +425,23 @@ function getLabelConfigMapFromObject(configObject) {
     return labelMap;
 }
 exports.getLabelConfigMapFromObject = getLabelConfigMapFromObject;
+function getSizeConfigMapFromObject(configObject) {
+    const sizeConfigObject = configObject['size-config'];
+    if (sizeConfigObject === undefined) {
+        return DEFAULT_SIZES;
+    }
+    const sizesConfig = new Map();
+    const sizesObject = JSON.parse(sizeConfigObject);
+    for (const [key, value] of Object.entries(sizesObject)) {
+        const keyNum = Number(key);
+        if (Number.isNaN(keyNum)) {
+            throw Error(`found non-number as key in size config ${key} (keys of size config should always be a valid number)`);
+        }
+        sizesConfig.set(keyNum, value);
+    }
+    return sizesConfig;
+}
+exports.getSizeConfigMapFromObject = getSizeConfigMapFromObject;
 function toMatchConfig(config) {
     const changedFilesConfig = (0, changedFiles_1.toChangedFilesMatchConfig)(config);
     const branchConfig = (0, branch_1.toBranchMatchConfig)(config);
@@ -436,6 +475,27 @@ function checkMatch(changedFiles, matchConfig) {
     }
     return true;
 }
+function checkSizeConfigs(changedFiles, sizeConfigs) {
+    let label = undefined;
+    let totalSize = 0;
+    for (const file of changedFiles) {
+        totalSize += file.size;
+    }
+    const sortedSizeKeys = [...sizeConfigs.keys()].sort((a, b) => {
+        return a - b;
+    });
+    for (const lines of sortedSizeKeys) {
+        if (totalSize >= lines) {
+            label = `size/${sizeConfigs.get(lines)}`;
+        }
+    }
+    if (label === undefined) {
+        core.warning(`The size of the PR is smaller than the smallest configured size ${sortedSizeKeys.slice(-1)}. Setting size to XXS.`);
+        label = 'size/XXS';
+    }
+    return label;
+}
+exports.checkSizeConfigs = checkSizeConfigs;
 // equivalent to "Array.some()" but expanded for debugging and clarity
 function checkAny(matchConfigs, changedFiles) {
     core.debug(`  checking "any" patterns`);
diff --git a/src/changedFiles.ts b/src/changedFiles.ts
index cd83f3d62..34850aed8 100644
--- a/src/changedFiles.ts
+++ b/src/changedFiles.ts
@@ -1,6 +1,7 @@
 import * as core from '@actions/core';
 import * as github from '@actions/github';
 import {Minimatch} from 'minimatch';
+import {PrFileType} from './labeler';
 
 export interface ChangedFilesMatchConfig {
   changedFiles?: string[];
@@ -11,7 +12,7 @@ type ClientType = ReturnType<typeof github.getOctokit>;
 export async function getChangedFiles(
   client: ClientType,
   prNumber: number
-): Promise<string[]> {
+): Promise<PrFileType[]> {
   const listFilesOptions = client.rest.pulls.listFiles.endpoint.merge({
     owner: github.context.repo.owner,
     repo: github.context.repo.repo,
@@ -19,7 +20,12 @@ export async function getChangedFiles(
   });
 
   const listFilesResponse = await client.paginate(listFilesOptions);
-  const changedFiles = listFilesResponse.map((f: any) => f.filename);
+  const changedFiles = listFilesResponse.map((f: any) => {
+    return {
+      name: f.filename as string,
+      size: (f.additions + f.deletions + f.changes) as number
+    };
+  });
 
   core.debug('found changed files:');
   for (const file of changedFiles) {
@@ -49,11 +55,11 @@ function printPattern(matcher: Minimatch): string {
   return (matcher.negate ? '!' : '') + matcher.pattern;
 }
 
-function isAnyMatch(changedFile: string, matchers: Minimatch[]): boolean {
+function isAnyMatch(changedFile: PrFileType, matchers: Minimatch[]): boolean {
   core.debug(`    matching patterns against file ${changedFile}`);
   for (const matcher of matchers) {
     core.debug(`     - ${printPattern(matcher)}`);
-    if (matcher.match(changedFile)) {
+    if (matcher.match(changedFile.name)) {
       core.debug(`    ${printPattern(matcher)} matched`);
       return true;
     }
@@ -63,11 +69,11 @@ function isAnyMatch(changedFile: string, matchers: Minimatch[]): boolean {
   return false;
 }
 
-function isAllMatch(changedFile: string, matchers: Minimatch[]): boolean {
+function isAllMatch(changedFile: PrFileType, matchers: Minimatch[]): boolean {
   core.debug(`    matching patterns against file ${changedFile}`);
   for (const matcher of matchers) {
     core.debug(`     - ${printPattern(matcher)}`);
-    if (!matcher.match(changedFile)) {
+    if (!matcher.match(changedFile.name)) {
       core.debug(`    ${printPattern(matcher)} did not match`);
       return false;
     }
@@ -78,7 +84,7 @@ function isAllMatch(changedFile: string, matchers: Minimatch[]): boolean {
 }
 
 export function checkAnyChangedFiles(
-  changedFiles: string[],
+  changedFiles: PrFileType[],
   globs: string[]
 ): boolean {
   const matchers = globs.map(g => new Minimatch(g));
@@ -94,7 +100,7 @@ export function checkAnyChangedFiles(
 }
 
 export function checkAllChangedFiles(
-  changedFiles: string[],
+  changedFiles: PrFileType[],
   globs: string[]
 ): boolean {
   const matchers = globs.map(g => new Minimatch(g));
diff --git a/src/labeler.ts b/src/labeler.ts
index ca6a113b8..e063cbb24 100644
--- a/src/labeler.ts
+++ b/src/labeler.ts
@@ -4,16 +4,16 @@ import * as yaml from 'js-yaml';
 
 import {
   ChangedFilesMatchConfig,
-  getChangedFiles,
-  toChangedFilesMatchConfig,
   checkAllChangedFiles,
-  checkAnyChangedFiles
+  checkAnyChangedFiles,
+  getChangedFiles,
+  toChangedFilesMatchConfig
 } from './changedFiles';
 import {
-  checkAnyBranch,
+  BranchMatchConfig,
   checkAllBranch,
-  toBranchMatchConfig,
-  BranchMatchConfig
+  checkAnyBranch,
+  toBranchMatchConfig
 } from './branch';
 
 export type BaseMatchConfig = BranchMatchConfig & ChangedFilesMatchConfig;
@@ -23,15 +23,34 @@ export type MatchConfig = {
   all?: BaseMatchConfig[];
 };
 
+export type LabelerConfig = {
+  labels: Map<string, MatchConfig[]>;
+  size: Map<number, string>;
+};
+
+export type PrFileType = {
+  name: string;
+  size: number;
+};
+
 type ClientType = ReturnType<typeof github.getOctokit>;
 
 const ALLOWED_CONFIG_KEYS = ['changed-files', 'head-branch', 'base-branch'];
+const DEFAULT_SIZES = new Map([
+  [0, 'XS'],
+  [10, 'S'],
+  [30, 'M'],
+  [100, 'L'],
+  [500, 'XL'],
+  [1000, 'XXL']
+]);
 
 export async function run() {
   try {
     const token = core.getInput('repo-token');
     const configPath = core.getInput('configuration-path', {required: true});
     const syncLabels = core.getBooleanInput('sync-labels');
+    const checkSizeEnabled = core.getBooleanInput('check-size');
 
     const prNumber = getPrNumber();
     if (!prNumber) {
@@ -48,15 +67,12 @@ export async function run() {
     });
 
     core.debug(`fetching changed files for pr #${prNumber}`);
-    const changedFiles: string[] = await getChangedFiles(client, prNumber);
-    const labelConfigs: Map<string, MatchConfig[]> = await getMatchConfigs(
-      client,
-      configPath
-    );
+    const changedFiles: PrFileType[] = await getChangedFiles(client, prNumber);
+    const labelerConfigs: LabelerConfig = await getConfigs(client, configPath);
 
     const labels: string[] = [];
     const labelsToRemove: string[] = [];
-    for (const [label, configs] of labelConfigs.entries()) {
+    for (const [label, configs] of labelerConfigs.labels.entries()) {
       core.debug(`processing ${label}`);
       if (checkMatchConfigs(changedFiles, configs)) {
         labels.push(label);
@@ -65,6 +81,11 @@ export async function run() {
       }
     }
 
+    if (checkSizeEnabled) {
+      const sizeLabel = checkSizeConfigs(changedFiles, labelerConfigs.size);
+      labels.push(sizeLabel);
+    }
+
     if (labels.length > 0) {
       await addLabels(client, prNumber, labels);
     }
@@ -87,10 +108,10 @@ function getPrNumber(): number | undefined {
   return pullRequest.number;
 }
 
-async function getMatchConfigs(
+async function getConfigs(
   client: ClientType,
   configurationPath: string
-): Promise<Map<string, MatchConfig[]>> {
+): Promise<LabelerConfig> {
   const configurationContent: string = await fetchContent(
     client,
     configurationPath
@@ -99,8 +120,11 @@ async function getMatchConfigs(
   // loads (hopefully) a `{[label:string]: MatchConfig[]}`, but is `any`:
   const configObject: any = yaml.load(configurationContent);
 
-  // transform `any` => `Map<string,MatchConfig[]>` or throw if yaml is malformed:
-  return getLabelConfigMapFromObject(configObject);
+  return {
+    // transform `any` => `Map<string,MatchConfig[]>` or throw if yaml is malformed:
+    labels: getLabelConfigMapFromObject(configObject),
+    size: getSizeConfigMapFromObject(configObject)
+  };
 }
 
 async function fetchContent(
@@ -120,9 +144,10 @@ async function fetchContent(
 export function getLabelConfigMapFromObject(
   configObject: any
 ): Map<string, MatchConfig[]> {
+  const labelConfigObject = configObject['label-config'];
   const labelMap: Map<string, MatchConfig[]> = new Map();
-  for (const label in configObject) {
-    const configOptions = configObject[label];
+  for (const label in labelConfigObject) {
+    const configOptions = labelConfigObject[label];
     if (
       !Array.isArray(configOptions) ||
       !configOptions.every(opts => typeof opts === 'object')
@@ -174,6 +199,28 @@ export function getLabelConfigMapFromObject(
   return labelMap;
 }
 
+export function getSizeConfigMapFromObject(
+  configObject: any
+): Map<number, string> {
+  const sizeConfigObject = configObject['size-config'];
+  if (sizeConfigObject === undefined) {
+    return DEFAULT_SIZES;
+  }
+
+  const sizesConfig: Map<number, string> = new Map();
+  const sizesObject = JSON.parse(sizeConfigObject);
+  for (const [key, value] of Object.entries(sizesObject)) {
+    const keyNum = Number(key);
+    if (Number.isNaN(keyNum)) {
+      throw Error(
+        `found non-number as key in size config ${key} (keys of size config should always be a valid number)`
+      );
+    }
+    sizesConfig.set(keyNum, value as string);
+  }
+  return sizesConfig;
+}
+
 export function toMatchConfig(config: any): BaseMatchConfig {
   const changedFilesConfig = toChangedFilesMatchConfig(config);
   const branchConfig = toBranchMatchConfig(config);
@@ -185,7 +232,7 @@ export function toMatchConfig(config: any): BaseMatchConfig {
 }
 
 export function checkMatchConfigs(
-  changedFiles: string[],
+  changedFiles: PrFileType[],
   matchConfigs: MatchConfig[]
 ): boolean {
   for (const config of matchConfigs) {
@@ -198,7 +245,10 @@ export function checkMatchConfigs(
   return true;
 }
 
-function checkMatch(changedFiles: string[], matchConfig: MatchConfig): boolean {
+function checkMatch(
+  changedFiles: PrFileType[],
+  matchConfig: MatchConfig
+): boolean {
   if (!Object.keys(matchConfig).length) {
     core.debug(`  no "any" or "all" patterns to check`);
     return false;
@@ -219,10 +269,39 @@ function checkMatch(changedFiles: string[], matchConfig: MatchConfig): boolean {
   return true;
 }
 
+export function checkSizeConfigs(
+  changedFiles: PrFileType[],
+  sizeConfigs: Map<number, string>
+): string {
+  let label: string | undefined = undefined;
+  let totalSize = 0;
+  for (const file of changedFiles) {
+    totalSize += file.size;
+  }
+  const sortedSizeKeys = [...sizeConfigs.keys()].sort((a, b) => {
+    return a - b;
+  });
+  for (const lines of sortedSizeKeys) {
+    if (totalSize >= lines) {
+      label = `size/${sizeConfigs.get(lines)}`;
+    }
+  }
+  if (label === undefined) {
+    core.warning(
+      `The size of the PR is smaller than the smallest configured size ${sortedSizeKeys.slice(
+        -1
+      )}. Setting size to XXS.`
+    );
+    label = 'size/XXS';
+  }
+
+  return label;
+}
+
 // equivalent to "Array.some()" but expanded for debugging and clarity
 export function checkAny(
   matchConfigs: BaseMatchConfig[],
-  changedFiles: string[]
+  changedFiles: PrFileType[]
 ): boolean {
   core.debug(`  checking "any" patterns`);
   if (
@@ -260,7 +339,7 @@ export function checkAny(
 // equivalent to "Array.every()" but expanded for debugging and clarity
 export function checkAll(
   matchConfigs: BaseMatchConfig[],
-  changedFiles: string[]
+  changedFiles: PrFileType[]
 ): boolean {
   core.debug(`  checking "all" patterns`);
   if (