diff --git a/geometry.go b/geometry.go
index 98fd8c1e44a8ba591621a639486133a9e427d4a1..7e1792433500a0fd1165fbdd1ea064097361c610 100644
--- a/geometry.go
+++ b/geometry.go
@@ -358,14 +358,9 @@ func (c Circle) Norm() Circle {
 	}
 }
 
-// Diameter returns the diameter of the Circle.
-func (c Circle) Diameter() float64 {
-	return c.Radius * 2
-}
-
 // Area returns the area of the Circle.
 func (c Circle) Area() float64 {
-	return math.Pi * c.Diameter()
+	return math.Pi * c.Radius * 2
 }
 
 // Moved returns the Circle moved by the given vector delta.
diff --git a/geometry_test.go b/geometry_test.go
index 37f42292a81359b7d9bc476a6e32c2b1682fa7b3..3bebbbe45f684545c6122c7f0be321543d2b095c 100644
--- a/geometry_test.go
+++ b/geometry_test.go
@@ -191,42 +191,6 @@ func TestCircle_Norm(t *testing.T) {
 	}
 }
 
-func TestCircle_Diameter(t *testing.T) {
-	type fields struct {
-		radius float64
-		center pixel.Vec
-	}
-	tests := []struct {
-		name   string
-		fields fields
-		want   float64
-	}{
-		{
-			name:   "Circle.Diameter(): positive radius",
-			fields: fields{radius: 10, center: pixel.V(0, 0)},
-			want:   20,
-		},
-		{
-			name:   "Circle.Diameter(): zero radius",
-			fields: fields{radius: 0, center: pixel.V(0, 0)},
-			want:   0,
-		},
-		{
-			name:   "Circle.Diameter(): negative radius",
-			fields: fields{radius: -5, center: pixel.V(0, 0)},
-			want:   -10,
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			c := pixel.C(tt.fields.radius, tt.fields.center)
-			if got := c.Diameter(); got != tt.want {
-				t.Errorf("Circle.Diameter() = %v, want %v", got, tt.want)
-			}
-		})
-	}
-}
-
 func TestCircle_Area(t *testing.T) {
 	type fields struct {
 		radius float64