diff --git a/.changeset/hex-alpha-full-precision.md b/.changeset/hex-alpha-full-precision.md
new file mode 100644
index 00000000..d31caacd
--- /dev/null
+++ b/.changeset/hex-alpha-full-precision.md
@@ -0,0 +1,5 @@
+---
+"chroma-js": patch
+---
+
+Preserve full alpha precision when parsing `#rrggbbaa` / `#rgba` hex colors. `hex2rgb` rounded the alpha channel to two decimals, so 136 of 256 alpha bytes did not round-trip (for example `chroma('#ff000088').hex()` returned `#ff000087`). Alpha is now parsed exactly as `aa / 255`, matching the RGB channels and CSS Color 4.
diff --git a/src/io/hex/hex2rgb.js b/src/io/hex/hex2rgb.js
index e1f43b4b..02974503 100644
--- a/src/io/hex/hex2rgb.js
+++ b/src/io/hex/hex2rgb.js
@@ -42,7 +42,7 @@ const hex2rgb = (hex) => {
         const r = (u >> 24) & 0xff;
         const g = (u >> 16) & 0xff;
         const b = (u >> 8) & 0xff;
-        const a = Math.round(((u & 0xff) / 0xff) * 100) / 100;
+        const a = (u & 0xff) / 0xff;
         return [r, g, b, a];
     }
 
diff --git a/test/alpha.test.js b/test/alpha.test.js
index e398de80..f5621e18 100644
--- a/test/alpha.test.js
+++ b/test/alpha.test.js
@@ -35,8 +35,8 @@ describe('Tests for the alpha channel', () => {
     it('parsing hex rgba colors', () => {
         const color = chroma('#ff00004d');
         expect(color.name()).toBe('red');
-        expect(color.alpha()).toBe(0.3);
-        expect(color.rgba()).toEqual([255, 0, 0, 0.3]);
+        expect(color.alpha()).toBe(0x4d / 255);
+        expect(color.rgba()).toEqual([255, 0, 0, 0x4d / 255]);
     });
 
     it('parsing rgba colors', () => {
diff --git a/test/contrast.test.js b/test/contrast.test.js
index 51ec8be0..776b7169 100644
--- a/test/contrast.test.js
+++ b/test/contrast.test.js
@@ -43,10 +43,8 @@ describe('Testing contrast ratio with APCA', () => {
     });
 
     it('contrast with alpha', () => {
-        // todo: there's a slight difference to the values shown in the APCA demo
-        // when computing contrast between colors with alpha
-        expect(+contrastAPCA('#00000044', 'white').toFixed(1)).toBe(37.3); // 36.7
-        expect(+contrastAPCA('#ffffffc0', 'black').toFixed(1)).toBe(-68); // -68.6
+        expect(+contrastAPCA('#00000044', 'white').toFixed(1)).toBe(36.7);
+        expect(+contrastAPCA('#ffffffc0', 'black').toFixed(1)).toBe(-68.6);
     });
 
     it('inverse contrast', () => {
diff --git a/test/io/hex2rgb.test.js b/test/io/hex2rgb.test.js
index c93cea9d..1c931d1f 100644
--- a/test/io/hex2rgb.test.js
+++ b/test/io/hex2rgb.test.js
@@ -116,29 +116,29 @@ describe('Testing HEX2RGB color conversions', () => {
         ],
         'parse different #rrggbbaa HEX colors': [
             [0, 0, 0, 0],
-            [255, 255, 255, 0.5],
-            [255, 0, 0, 0.25],
-            [0, 255, 0, 0.75],
+            [255, 255, 255, 128 / 255],
+            [255, 0, 0, 64 / 255],
+            [0, 255, 0, 192 / 255],
             [255, 0, 255, 1]
         ],
         'parse different rrggbbaa HEX colors without #': [
             [0, 0, 0, 0],
-            [255, 255, 255, 0.5],
-            [255, 0, 0, 0.25],
-            [0, 255, 0, 0.75],
+            [255, 255, 255, 128 / 255],
+            [255, 0, 0, 64 / 255],
+            [0, 255, 0, 192 / 255],
             [255, 0, 255, 1]
         ],
         'parse different #rgba HEX colors': [
             [0, 0, 0, 0],
-            [255, 255, 255, 0.53],
-            [255, 0, 0, 0.27],
+            [255, 255, 255, 136 / 255],
+            [255, 0, 0, 68 / 255],
             [0, 255, 0, 0.8],
             [255, 0, 255, 1]
         ],
         'parse different rgba HEX colors without #': [
             [0, 0, 0, 0],
-            [255, 255, 255, 0.53],
-            [255, 0, 0, 0.27],
+            [255, 255, 255, 136 / 255],
+            [255, 0, 0, 68 / 255],
             [0, 255, 0, 0.8],
             [255, 0, 255, 1]
         ]