diff --git a/package-lock.json b/package-lock.json
index fc7b7e1..301e82f 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -154,7 +154,6 @@
       "resolved": "https://registry.npmjs.org/react/-/react-19.1.1.tgz",
       "integrity": "sha512-w8nqGImo45dmMIfljjMwOGtbmC/mk4CMYhWIicdSflH91J9TyCyczcPFXJzrZ/ZXcgGRFeP6BU0BEJTw6tZdfQ==",
       "license": "MIT",
-      "peer": true,
       "engines": {
         "node": ">=0.10.0"
       }
@@ -216,7 +215,6 @@
       "integrity": "sha512-2BCOP7TN8M+gVDj7/ht3hsaO/B/n5oDbiAyyvnRlNOs+u1o+JWNYTQrmpuNp1/Wq2gcFrI01JAW+paEKDMx/CA==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@babel/code-frame": "^7.27.1",
         "@babel/generator": "^7.28.3",
@@ -1495,7 +1493,6 @@
       "resolved": "https://registry.npmjs.org/@iiif/parser/-/parser-2.2.1.tgz",
       "integrity": "sha512-pHz4WR+1LXm9VglHmcPKthqOkDRB8YzbDkGJE82wgQyZyh8l0iXQcq9MysSqxK5GuKi8qBaOTTUdiFlb1r2ARA==",
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@iiif/presentation-2": "^1.0.4",
         "@iiif/presentation-3": "^2.2.2",
@@ -1517,7 +1514,6 @@
       "resolved": "https://registry.npmjs.org/@iiif/presentation-3/-/presentation-3-2.2.3.tgz",
       "integrity": "sha512-xCLbUr9euqegsrxGe65M2fWbv6gKpiUhHXCpOn+V+qtawkMbOSNWbYOISo2aLQdYVg4DGYD0g2bMzSCF33uNOQ==",
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@types/geojson": "^7946.0.10"
       }
@@ -4447,7 +4443,6 @@
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       "devOptional": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "csstype": "^3.0.2"
       }
@@ -4458,7 +4453,6 @@
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       "devOptional": true,
       "license": "MIT",
-      "peer": true,
       "peerDependencies": {
         "@types/react": "^19.0.0"
       }
@@ -4860,7 +4854,6 @@
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       "dev": true,
       "license": "MIT",
-      "peer": true,
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -5323,7 +5316,6 @@
         }
       ],
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "baseline-browser-mapping": "^2.8.2",
         "caniuse-lite": "^1.0.30001741",
@@ -6356,7 +6348,6 @@
       "dev": true,
       "hasInstallScript": true,
       "license": "MIT",
-      "peer": true,
       "bin": {
         "esbuild": "bin/esbuild"
       },
@@ -6426,7 +6417,6 @@
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       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@eslint-community/eslint-utils": "^4.8.0",
         "@eslint-community/regexpp": "^4.12.1",
@@ -7916,7 +7906,6 @@
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       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@jest/core": "^29.7.0",
         "@jest/types": "^29.6.3",
@@ -8798,6 +8787,7 @@
       "resolved": "https://registry.npmjs.org/loose-envify/-/loose-envify-1.4.0.tgz",
       "integrity": "sha512-lyuxPGr/Wfhrlem2CL/UcnUc1zcqKAImBDzukY7Y5F/yQiNdko6+fRLevlw1HgMySw7f611UIY408EtxRSoK3Q==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "js-tokens": "^3.0.0 || ^4.0.0"
       },
@@ -10977,6 +10967,7 @@
       "resolved": "https://registry.npmjs.org/scheduler/-/scheduler-0.23.2.tgz",
       "integrity": "sha512-UOShsPwz7NrMUqhR6t0hWjFduvOzbtv7toDH1/hIrfRNIDBnnBWd0CwJTGvTpngVlmwGCdP9/Zl/tVrDqcuYzQ==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "loose-envify": "^1.1.0"
       }
@@ -12339,7 +12330,6 @@
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       "dev": true,
       "license": "MIT",
-      "peer": true,
       "engines": {
         "node": ">=12"
       },
@@ -12820,7 +12810,6 @@
       "integrity": "sha512-VGMpFQGUQWYT9LfnPcX8ouFojyrZ/2w3K5BucvxL/spdNehccKhB4jUyB1yBCXpr2XFm0jkECxgrpXBW2ipoAw==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@typescript-eslint/scope-manager": "8.44.0",
         "@typescript-eslint/types": "8.44.0",
@@ -13305,7 +13294,6 @@
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       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "esbuild": "^0.25.0",
         "fdir": "^6.4.4",
@@ -13399,7 +13387,6 @@
       "integrity": "sha512-5gTmgEY/sqK6gFXLIsQNH19lWb4ebPDLA4SdLP7dsWkIXHWlG66oPuVvXSGFPppYZz8ZDZq0dYYrbHfBCVUb1Q==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "engines": {
         "node": ">=12"
       },
diff --git a/src/calculator/v3.ts b/src/calculator/v3.ts
index 6e96291..1231fbd 100644
--- a/src/calculator/v3.ts
+++ b/src/calculator/v3.ts
@@ -31,7 +31,7 @@ export class Calculator extends Base {
     }
     super.size(v);
     const { region, size, upscale } = this._parsedInfo;
-    if (!upscale) {
+    if (!upscale && size.fit !== 'inside') {
       if (size.width > region.width || size.height > region.height) {
         throw new IIIFError('Requested size requires upscaling', {
           statusCode: 400
diff --git a/tests/v3/calculator.test.ts b/tests/v3/calculator.test.ts
index 0081e6f..56e03ca 100644
--- a/tests/v3/calculator.test.ts
+++ b/tests/v3/calculator.test.ts
@@ -154,6 +154,40 @@ describe('Calculator', () => {
       subject.region('pct:50,50,25,25').size('^512,384').rotation('45').quality('default').format('jpg', 600);
       assert.deepEqual(subject.info(), expected);
     });
+
+    it('allows best-fit sizing larger than source without upscaling error', () => {
+      subject = new Calculator({ width: 1024, height: 768 });
+
+      // !9000,9000 should not throw even though dimensions exceed source
+      assert.doesNotThrow(() => {
+        subject
+          .region('full')
+          .size('!9000,9000')
+          .rotation('0')
+          .quality('default')
+          .format('jpg');
+      }, IIIFError);
+
+      const result = subject.info();
+      assert.equal(result.size.fit, 'inside');
+      assert.equal(result.size.width, 9000);
+      assert.equal(result.size.height, 9000);
+      assert.equal(result.upscale, false);
+    });
+
+    it('throws upscaling error for exact size larger than source', () => {
+      subject = new Calculator({ width: 1024, height: 768 });
+
+      // 9000,9000 without ! should throw upscaling error
+      assert.throws(() => {
+        subject
+          .region('full')
+          .size('9000,9000')
+          .rotation('0')
+          .quality('default')
+          .format('jpg');
+      }, IIIFError);
+    });
   });
 
   describe('density', () => {