Wheel Offset & Fitment
Convert wheel offset to backspace and see how a new wheel changes inner clearance, poke and track width before you buy. Free fitment calculator.
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Offset and backspace
Offset (ET) is the distance from the wheel mounting face to the centre line, in mm. Backspace is the distance from the mounting face to the inner edge: backspace = width / 2 + offset.
- Positive offset pulls the wheel inboard
- A wider wheel adds half its extra width to each side
- Outer position shows how far the wheel pokes out
Check clearance before buying
Compare the current and new wheel to see whether you gain or lose inner clearance to the struts and brakes, and how much the wheel will poke out of the fender. Always confirm bolt pattern, centre bore and clearance on the car.
FAQ
There is no single answer: it depends on wheel width and the car. Use the calculator to keep inner clearance positive and poke reasonable, then verify on the vehicle.
Offset changes track width, not rolling diameter, so the speedometer is unaffected. Rolling diameter depends on tire size, not offset.
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