I always found it difficult to reconcile the two disparate worlds of print and on-screen design, mainly because of the different unit of measurements. Math and designers never quite go well together. In comes the Pixel Ruler from UI Stencils and suddenly my sketches make sense as on screen graphics. Now if only they would put some MM measurements on the other edge and I would gladly throw all my other rulers away. Buy yours today for USD 24 at UI Stencils.