This Offset Calculator allows you to compare how a new set of wheels will compare to those you already have on your car.
It's easy to get confused with widths, offsets and such, so hopefully this will make things a little simpler by giving you some guide measurements you can check on your car and see how much you're going to have to flare your arches to get those massive rims to fit 
Wheel width is measured in inches and can also be referred to as a 'J' value
Wheel offset is measured in mm and can also be refered to as an 'ET' value
For example, an 18 x 10J ET-15 wheel would be 18inches in diameter, 10 inches wide, with an offset of -15mm
The distance from the suspension strut to the inside edge of the wheel will be the same.
The outside edge of the wheel will be the same.
This calculator assumes 25mm = 1 inch
