diff --git a/src/ImageSharp/Formats/Heif/Av1/Av1BlockSize.cs b/src/ImageSharp/Formats/Heif/Av1/Av1BlockSize.cs
index c38f620c4..62c4ff59e 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Av1BlockSize.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Av1BlockSize.cs
@@ -72,7 +72,7 @@ internal enum Av1BlockSize : byte
 
     /// <summary>A block of samples, 64 samples wide and 16 samples high.</summary>
     Block64x16 = 21,
-    SizesAll = 22,
+    AllSizes = 22,
     SizeS = Block4x16,
     Invalid = 255,
     Largest = SizeS - 1,
diff --git a/src/ImageSharp/Formats/Heif/Av1/Av1BlockSizeExtensions.cs b/src/ImageSharp/Formats/Heif/Av1/Av1BlockSizeExtensions.cs
index 3c5ce9e59..6029d4fdd 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Av1BlockSizeExtensions.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Av1BlockSizeExtensions.cs
@@ -1,7 +1,6 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
-using SixLabors.ImageSharp.Formats.Heif.Av1.Quantization;
 using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
 
 namespace SixLabors.ImageSharp.Formats.Heif.Av1;
@@ -104,7 +103,7 @@ internal static class Av1BlockSizeExtensions
     {
         Av1BlockSize planeBlockSize = blockSize.GetSubsampled(subX, subY);
         Av1TransformSize uvTransformSize = Av1TransformSize.Invalid;
-        if (planeBlockSize < Av1BlockSize.SizesAll)
+        if (planeBlockSize < Av1BlockSize.AllSizes)
         {
             uvTransformSize = planeBlockSize.GetMaximumTransformSize();
         }
diff --git a/src/ImageSharp/Formats/Heif/Av1/Transform/Av1TransformTypeExtensions.cs b/src/ImageSharp/Formats/Heif/Av1/Transform/Av1TransformTypeExtensions.cs
index 48c14ba2a..c03b3b440 100644
--- a/src/ImageSharp/Formats/Heif/Av1/Transform/Av1TransformTypeExtensions.cs
+++ b/src/ImageSharp/Formats/Heif/Av1/Transform/Av1TransformTypeExtensions.cs
@@ -1,8 +1,6 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
-using System;
-
 namespace SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
 
 internal static class Av1TransformTypeExtensions
diff --git a/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1BlockSizeTests.cs b/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1BlockSizeTests.cs
new file mode 100644
index 000000000..79b32e92a
--- /dev/null
+++ b/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1BlockSizeTests.cs
@@ -0,0 +1,119 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Heif.Av1;
+using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
+
+namespace SixLabors.ImageSharp.Tests.Formats.Heif.Av1;
+
+[Trait("Format", "Avif")]
+public class Av1BlockSizeTests
+{
+    [Theory]
+    [MemberData(nameof(GetAllSizes))]
+    internal void GetWidthReturnsCorrectWidth(int s)
+    {
+        // Assign
+        Av1BlockSize blockSize = (Av1BlockSize)s;
+        int expectedWidth = blockSize switch
+        {
+            Av1BlockSize.Block4x4 or Av1BlockSize.Block4x8 or Av1BlockSize.Block4x16 => 4,
+            Av1BlockSize.Block8x4 or Av1BlockSize.Block8x8 or Av1BlockSize.Block8x16 or Av1BlockSize.Block8x32 => 8,
+            Av1BlockSize.Block16x4 or Av1BlockSize.Block16x8 or Av1BlockSize.Block16x16 or Av1BlockSize.Block16x32 or Av1BlockSize.Block16x64 => 16,
+            Av1BlockSize.Block32x8 or Av1BlockSize.Block32x16 or Av1BlockSize.Block32x32 or Av1BlockSize.Block32x64 => 32,
+            Av1BlockSize.Block64x16 or Av1BlockSize.Block64x32 or Av1BlockSize.Block64x64 or Av1BlockSize.Block64x128 => 64,
+            Av1BlockSize.Block128x64 or Av1BlockSize.Block128x128 => 128,
+            _ => -1
+        };
+
+        // Act
+        int actualWidth = blockSize.GetWidth();
+
+        // Assert
+        Assert.Equal(expectedWidth, actualWidth);
+    }
+
+    [Theory]
+    [MemberData(nameof(GetAllSizes))]
+    internal void GetHeightReturnsCorrectHeight(int s)
+    {
+        // Assign
+        Av1BlockSize blockSize = (Av1BlockSize)s;
+        int expectedHeight = blockSize switch
+        {
+            Av1BlockSize.Block4x4 or Av1BlockSize.Block8x4 or Av1BlockSize.Block16x4 => 4,
+            Av1BlockSize.Block4x8 or Av1BlockSize.Block8x8 or Av1BlockSize.Block16x8 or Av1BlockSize.Block32x8 => 8,
+            Av1BlockSize.Block4x16 or Av1BlockSize.Block8x16 or Av1BlockSize.Block16x16 or Av1BlockSize.Block32x16 or Av1BlockSize.Block64x16 => 16,
+            Av1BlockSize.Block8x32 or Av1BlockSize.Block16x32 or Av1BlockSize.Block32x32 or Av1BlockSize.Block64x32 => 32,
+            Av1BlockSize.Block16x64 or Av1BlockSize.Block32x64 or Av1BlockSize.Block64x64 or Av1BlockSize.Block128x64 => 64,
+            Av1BlockSize.Block64x128 or Av1BlockSize.Block128x128 => 128,
+            _ => -1
+        };
+
+        // Act
+        int actualHeight = blockSize.GetHeight();
+
+        // Assert
+        Assert.Equal(expectedHeight, actualHeight);
+    }
+
+    [Theory]
+    [MemberData(nameof(GetAllSizes))]
+    internal void GetSubSampledReturnsCorrectSize(int s)
+    {
+        if (s is 0 or 1 or 2 or 16 or 17)
+        {
+            // Exceptional values, skip for this generic test.
+            return;
+        }
+
+        // Assign
+        Av1BlockSize blockSize = (Av1BlockSize)s;
+        int originalWidth = blockSize.GetWidth();
+        int originalHeight = blockSize.GetHeight();
+
+        // Act
+        Av1BlockSize actualNoNo = blockSize.GetSubsampled(false, false);
+        Av1BlockSize actualYesNo = blockSize.GetSubsampled(true, false);
+        Av1BlockSize actualNoYes = blockSize.GetSubsampled(false, true);
+        Av1BlockSize actualYesYes = blockSize.GetSubsampled(true, true);
+
+        // Assert
+        Assert.Equal(originalWidth, actualNoNo.GetWidth());
+        Assert.Equal(originalHeight, actualNoNo.GetHeight());
+
+        if (actualYesNo != Av1BlockSize.Invalid)
+        {
+            Assert.Equal(originalWidth, actualYesNo.GetWidth() * 2);
+            Assert.Equal(originalHeight, actualYesNo.GetHeight());
+        }
+
+        if (actualNoYes != Av1BlockSize.Invalid)
+        {
+            Assert.Equal(originalWidth, actualNoYes.GetWidth());
+            Assert.Equal(originalHeight, actualNoYes.GetHeight() * 2);
+        }
+
+        Assert.Equal(originalWidth, actualYesYes.GetWidth() * 2);
+        Assert.Equal(originalHeight, actualYesYes.GetHeight() * 2);
+    }
+
+    public static TheoryData<int> GetAllSizes()
+    {
+        TheoryData<int> combinations = [];
+        for (int s = 0; s < (int)Av1BlockSize.AllSizes; s++)
+        {
+            combinations.Add(s);
+        }
+
+        return combinations;
+    }
+
+    private static int GetRatio(Av1BlockSize blockSize)
+    {
+        int width = blockSize.GetWidth();
+        int height = blockSize.GetHeight();
+        int ratio = width > height ? width / height : height / width;
+        return ratio;
+    }
+}
diff --git a/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1TransformSizeTests.cs b/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1TransformSizeTests.cs
new file mode 100644
index 000000000..d0740edc3
--- /dev/null
+++ b/tests/ImageSharp.Tests/Formats/Heif/Av1/Av1TransformSizeTests.cs
@@ -0,0 +1,152 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Heif.Av1;
+using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
+
+namespace SixLabors.ImageSharp.Tests.Formats.Heif.Av1;
+
+[Trait("Format", "Avif")]
+public class Av1TransformSizeTests
+{
+    [Theory]
+    [MemberData(nameof(GetAllSizes))]
+    internal void GetWidthReturnsCorrectWidth(int s)
+    {
+        // Assign
+        Av1TransformSize transformSize = (Av1TransformSize)s;
+        int expectedWidth = transformSize switch
+        {
+            Av1TransformSize.Size4x4 or Av1TransformSize.Size4x8 or Av1TransformSize.Size4x16 => 4,
+            Av1TransformSize.Size8x4 or Av1TransformSize.Size8x8 or Av1TransformSize.Size8x16 or Av1TransformSize.Size8x32 => 8,
+            Av1TransformSize.Size16x4 or Av1TransformSize.Size16x8 or Av1TransformSize.Size16x16 or Av1TransformSize.Size16x32 or Av1TransformSize.Size16x64 => 16,
+            Av1TransformSize.Size32x8 or Av1TransformSize.Size32x16 or Av1TransformSize.Size32x32 or Av1TransformSize.Size32x64 => 32,
+            Av1TransformSize.Size64x16 or Av1TransformSize.Size64x32 or Av1TransformSize.Size64x64 => 64,
+            _ => -1
+        };
+
+        // Act
+        int actualWidth = transformSize.GetWidth();
+
+        // Assert
+        Assert.Equal(expectedWidth, actualWidth);
+    }
+
+    [Theory]
+    [MemberData(nameof(GetAllSizes))]
+    internal void GetHeightReturnsCorrectHeight(int s)
+    {
+        // Assign
+        Av1TransformSize transformSize = (Av1TransformSize)s;
+        int expectedHeight = transformSize switch
+        {
+            Av1TransformSize.Size4x4 or Av1TransformSize.Size8x4 or Av1TransformSize.Size16x4 => 4,
+            Av1TransformSize.Size4x8 or Av1TransformSize.Size8x8 or Av1TransformSize.Size16x8 or Av1TransformSize.Size32x8 => 8,
+            Av1TransformSize.Size4x16 or Av1TransformSize.Size8x16 or Av1TransformSize.Size16x16 or Av1TransformSize.Size32x16 or Av1TransformSize.Size64x16 => 16,
+            Av1TransformSize.Size8x32 or Av1TransformSize.Size16x32 or Av1TransformSize.Size32x32 or Av1TransformSize.Size64x32 => 32,
+            Av1TransformSize.Size16x64 or Av1TransformSize.Size32x64 or Av1TransformSize.Size64x64 => 64,
+            _ => -1
+        };
+
+        // Act
+        int actualHeight = transformSize.GetHeight();
+
+        // Assert
+        Assert.Equal(expectedHeight, actualHeight);
+    }
+
+    [Theory]
+    [MemberData(nameof(GetAllSizes))]
+    internal void GetSubSizeReturnsCorrectRatio(int s)
+    {
+        // Assign
+        Av1TransformSize transformSize = (Av1TransformSize)s;
+        int ratio = GetRatio(transformSize);
+        int expectedRatio = (ratio == 4) ? 2 : 1;
+
+        // Act
+        Av1TransformSize actual = transformSize.GetSubSize();
+        int actualRatio = GetRatio(actual);
+
+        // Assert
+        Assert.Equal(expectedRatio, actualRatio);
+    }
+
+    [Theory]
+    [MemberData(nameof(GetAllSizes))]
+    internal void GetSquareSizeReturnsCorrectRatio(int s)
+    {
+        // Assign
+        Av1TransformSize transformSize = (Av1TransformSize)s;
+        int ratio = GetRatio(transformSize);
+        int expectedRatio = 1;
+        int expectedSize = Math.Min(transformSize.GetWidth(), transformSize.GetHeight());
+
+        // Act
+        Av1TransformSize actual = transformSize.GetSquareSize();
+        int actualRatio = GetRatio(actual);
+
+        // Assert
+        Assert.Equal(expectedRatio, actualRatio);
+        Assert.Equal(expectedSize, actual.GetWidth());
+        Assert.Equal(expectedSize, actual.GetHeight());
+    }
+
+    [Theory]
+    [MemberData(nameof(GetAllSizes))]
+    internal void GetSquareUpSizeReturnsCorrectRatio(int s)
+    {
+        // Assign
+        Av1TransformSize transformSize = (Av1TransformSize)s;
+        int ratio = GetRatio(transformSize);
+        int expectedRatio = 1;
+        int expectedSize = Math.Max(transformSize.GetWidth(), transformSize.GetHeight());
+
+        // Act
+        Av1TransformSize actual = transformSize.GetSquareUpSize();
+        int actualRatio = GetRatio(actual);
+
+        // Assert
+        Assert.Equal(expectedRatio, actualRatio);
+        Assert.Equal(expectedSize, actual.GetWidth());
+        Assert.Equal(expectedSize, actual.GetHeight());
+    }
+
+    [Theory]
+    [MemberData(nameof(GetAllSizes))]
+    internal void ToBlockSizeReturnsSameWidthAndHeight(int s)
+    {
+        // Assign
+        Av1TransformSize transformSize = (Av1TransformSize)s;
+        int transformWidth = transformSize.GetWidth();
+        int transformHeight = transformSize.GetHeight();
+
+        // Act
+        Av1BlockSize blockSize = transformSize.ToBlockSize();
+        int blockWidth = blockSize.GetWidth();
+        int blockHeight = blockSize.GetHeight();
+
+        // Assert
+        Assert.Equal(transformWidth, blockWidth);
+        Assert.Equal(transformHeight, blockHeight);
+    }
+
+    public static TheoryData<int> GetAllSizes()
+    {
+        TheoryData<int> combinations = [];
+        for (int s = 0; s < (int)Av1TransformSize.AllSizes; s++)
+        {
+            combinations.Add(s);
+        }
+
+        return combinations;
+    }
+
+    private static int GetRatio(Av1TransformSize transformSize)
+    {
+        int width = transformSize.GetWidth();
+        int height = transformSize.GetHeight();
+        int ratio = width > height ? width / height : height / width;
+        return ratio;
+    }
+}