diff --git a/Source/Core/Geometry/EarClipPolygon.cs b/Source/Core/Geometry/EarClipPolygon.cs
index 9dac3255..23750b9a 100755
--- a/Source/Core/Geometry/EarClipPolygon.cs
+++ b/Source/Core/Geometry/EarClipPolygon.cs
@@ -73,22 +73,21 @@ namespace CodeImp.DoomBuilder.Geometry
 		// This calculates the area
 		public float CalculateArea()
 		{
-			// Multiply the x coordinate of each vertex by the y coordinate of the next vertex.
-			// Multiply the y coordinate of each vertex by the x coordinate of the next vertex.
-			// Subtract these.
-			float result = 0.0f;
-			int firstcalculated = 0;
-			LinkedListNode<EarClipVertex> n1 = base.First;
-			while(firstcalculated < 2)
-			{
-				LinkedListNode<EarClipVertex> n2 = n1.Next ?? base.First;
-				float a = n1.Value.Position.x * n2.Value.Position.y;
-				float b = n1.Value.Position.y * n2.Value.Position.x;
-				result += a - b;
-				n1 = n2;
-				if(n2 == base.First) firstcalculated++;
-			}
-			return Math.Abs(result / 2.0f);
+            float area = 0;
+            LinkedListNode<EarClipVertex> v = First;
+            do
+            {
+
+                EarClipVertex v1 = v.Value;
+                EarClipVertex v2 = (v.Next != null) ? v.Next.Value : First.Value;
+
+                area += (v2.Position.x + v1.Position.x) * (v2.Position.y - v1.Position.y);
+
+                v = v.Next;
+
+            }
+            while (v != null);
+			return Math.Abs(area * 0.5f);
 		}
 		
 		// This creates a bounding box from the outer polygon