diff --git a/lib/OpenLayers/Control/ZoomBox.js b/lib/OpenLayers/Control/ZoomBox.js
index 217a90a434..f8cea39bed 100644
--- a/lib/OpenLayers/Control/ZoomBox.js
+++ b/lib/OpenLayers/Control/ZoomBox.js
@@ -83,8 +83,8 @@ OpenLayers.Control.ZoomBox = OpenLayers.Class(OpenLayers.Control, {
                 bounds = new OpenLayers.Bounds(minXY.lon, minXY.lat,
                                                maxXY.lon, maxXY.lat);
             } else {
-                var pixWidth = Math.abs(position.right-position.left);
-                var pixHeight = Math.abs(position.top-position.bottom);
+                var pixWidth = position.right - position.left;
+                var pixHeight = position.bottom - position.top;
                 var zoomFactor = Math.min((this.map.size.h / pixHeight),
                     (this.map.size.w / pixWidth));
                 var extent = this.map.getExtent();
@@ -103,10 +103,10 @@ OpenLayers.Control.ZoomBox = OpenLayers.Class(OpenLayers.Control, {
                 oldRes = this.map.getResolution(),
                 newRes = this.map.getResolutionForZoom(zoom),
                 zoomOriginPx = {
-                    x: targetCenterPx.x +
-                        (targetCenterPx.x - centerPx.x) * newRes / oldRes,
-                    y: targetCenterPx.y +
-                        (targetCenterPx.y - centerPx.y) * newRes / oldRes
+                    x: (oldRes * targetCenterPx.x - newRes * centerPx.x) /
+                        (oldRes - newRes),
+                    y: (oldRes * targetCenterPx.y - newRes * centerPx.y) /
+                        (oldRes - newRes)
                 };
             this.map.zoomTo(zoom, zoomOriginPx);
             if (lastZoom == this.map.getZoom() && this.alwaysZoom == true){