Can any one recomend a good Wheel offset calculator ?

as one of my winter mods, is to change my wheels to something lighter, and more in keeping with the style of my 7

I currently run capri 7j alloys that are very heavy (anyone know what offset they are as they dont say on the wheel??)
but im thinking more on the line of superlights/minilights

regards

Steve

http://www.1010tires.com/WheelOffsetCalculator.asp

I did make one and post it up, but it seems to have gone...
Old post here

7" Capri wheels almost certainly ET5 which gives the same backspace as ET19 on a 6"