diff --git a/GPU/Common/DrawEngineCommon.cpp b/GPU/Common/DrawEngineCommon.cpp
index be411b648ba7..e005110d8a69 100644
--- a/GPU/Common/DrawEngineCommon.cpp
+++ b/GPU/Common/DrawEngineCommon.cpp
@@ -219,15 +219,17 @@ void DrawEngineCommon::UpdatePlanes() {
 	Vec2f minViewport = (minOffset_ - Vec2f(gstate.getViewportXCenter(), gstate.getViewportYCenter())) * inverseViewportScale;
 	Vec2f maxViewport = (maxOffset_ - Vec2f(gstate.getViewportXCenter(), gstate.getViewportYCenter())) * inverseViewportScale;
 
+	Vec2f viewportInvSize = Vec2f(1.0f / (maxViewport.x - minViewport.x), 1.0f / (maxViewport.y - minViewport.y));
+
 	Lin::Matrix4x4 applyViewport{};
 	// Scale to the viewport's size.
-	applyViewport.xx = 2.0f / (maxViewport.x - minViewport.x);
-	applyViewport.yy = 2.0f / (maxViewport.y - minViewport.y);
+	applyViewport.xx = 2.0f * viewportInvSize.x;
+	applyViewport.yy = 2.0f * viewportInvSize.y;
 	applyViewport.zz = 1.0f;
 	applyViewport.ww = 1.0f;
 	// And offset to the viewport's centers.
-	applyViewport.wx = -(maxViewport.x + minViewport.x) / (maxViewport.x - minViewport.x);
-	applyViewport.wy = -(maxViewport.y + minViewport.y) / (maxViewport.y - minViewport.y);
+	applyViewport.wx = -(maxViewport.x + minViewport.x) * viewportInvSize.x;
+	applyViewport.wy = -(maxViewport.y + minViewport.y) * viewportInvSize.y;
 
 	float mtx[16];
 	Matrix4ByMatrix4(mtx, worldviewproj, applyViewport.m);