How to read the result?
The offset (ET) is the distance between the wheel's mounting face on the hub and the centre line of the wheel. The lower the ET, the further out the wheel sits; the higher it is, the further in it sits. A wider wheel extends on both sides at once: that is why we compare the inner and outer edges, not just the ET.
The verdict is for guidance only: the actual space depends on your vehicle (calipers, shock absorbers, wheel arches, ride height, tyre size). Always have a fitting approved by a professional. You will find the original offset on your vehicle page (search by make).
Frequently asked questions
How do I calculate the offset difference between two wheels?
Convert the width of each wheel to millimetres (1 inch = 25.4 mm). The inner edge is at width/2 + ET from the mounting face, the outer edge at width/2 − ET. The difference between the two wheels shows how much closer the wheel gets to the suspension and how much further it sticks out of the wheel arch.
Does a wheel spacer change the offset?
Yes: a 10 mm wheel spacer reduces the effective offset by 10 mm (ET45 becomes ET35). The wheel moves 10 mm further out and 10 mm further from the suspension.
What offset difference is acceptable?
There is no universal figure: it all depends on the space available in the wheel well and around the calipers. In practice, a few millimetres almost always fit; beyond about ten millimetres, check on the vehicle (steering lock, suspension travel, wheel arch).
Where can I find a wheel's width and offset?
They are stamped on the back of the wheel or between the spokes, in the form “7.5Jx17 ET45”: 7.5 inches wide, 17 inches in diameter, 45 mm offset.