diff --git a/src/index.ts b/src/index.ts
index d1858c1..ff2ab2d 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -10,6 +10,7 @@ import { isGradient, resolveGradient } from './js/css-gradient';
 import { cssVar } from './js/css-var';
 import {
   extractDashedIdent,
+  isAbsoluteFontSize,
   isAbsoluteSizeOrLength,
   isColor,
   resolveLengthInPixels,
@@ -23,6 +24,7 @@ export const utils = {
   cssCalc,
   cssVar,
   extractDashedIdent,
+  isAbsoluteFontSize,
   isAbsoluteSizeOrLength,
   isColor,
   isGradient,
diff --git a/src/js/util.ts b/src/js/util.ts
index 7c4d93c..0ca502c 100644
--- a/src/js/util.ts
+++ b/src/js/util.ts
@@ -461,3 +461,28 @@ export const isAbsoluteSizeOrLength = (
   }
   return value === 0;
 };
+
+/**
+ * is absolute font size
+ * @param value - value
+ * @returns result
+ */
+export const isAbsoluteFontSize = (value: unknown): boolean => {
+  if (isString(value)) {
+    const size = value.toLowerCase().trim() as string;
+    if (/^[a-z-]+$/.test(size)) {
+      return absoluteFontSize.has(size);
+    } else {
+      const [, val, unit] = /^(\d+(?:\.\d+)?|\.\d+)([a-z-]+)?$/.exec(
+        size
+      ) as RegExpExecArray;
+      if (unit) {
+        return absoluteLength.has(unit);
+      } else if (val) {
+        const num = parseFloat(val);
+        return num === 0;
+      }
+    }
+  }
+  return false;
+};
diff --git a/test/util.test.ts b/test/util.test.ts
index b118465..c6e38d2 100644
--- a/test/util.test.ts
+++ b/test/util.test.ts
@@ -880,3 +880,62 @@ describe('is absolute size or length', () => {
     assert.strictEqual(res, true, 'result');
   });
 });
+
+describe('is absolute font size', () => {
+  const func = util.isAbsoluteFontSize;
+
+  it('should get false', () => {
+    const res = func('foo');
+    assert.strictEqual(res, false, 'result');
+  });
+
+  it('should get false', () => {
+    const res = func('smaller');
+    assert.strictEqual(res, false, 'result');
+  });
+
+  it('should get true', () => {
+    const res = func('medium');
+    assert.strictEqual(res, true, 'result');
+  });
+
+  it('should get false', () => {
+    const res = func('1em');
+    assert.strictEqual(res, false, 'result');
+  });
+
+  it('should get false', () => {
+    const res = func('1rem');
+    assert.strictEqual(res, false, 'result');
+  });
+
+  it('should get true', () => {
+    const res = func('1px');
+    assert.strictEqual(res, true, 'result');
+  });
+
+  it('should get true', () => {
+    const res = func('1pt');
+    assert.strictEqual(res, true, 'result');
+  });
+
+  it('should get false', () => {
+    const res = func('1');
+    assert.strictEqual(res, false, 'result');
+  });
+
+  it('should get true', () => {
+    const res = func('0');
+    assert.strictEqual(res, true, 'result');
+  });
+
+  it('should get true', () => {
+    const res = func('0.0');
+    assert.strictEqual(res, true, 'result');
+  });
+
+  it('should get true', () => {
+    const res = func('.0');
+    assert.strictEqual(res, true, 'result');
+  });
+});