Wheel offset calculator
Enter your current wheel and the one you’re considering — rim width and offset (ET). See how far the new wheel moves toward the suspension and toward the fender, and whether it should fit.
Start from your car factory wheels
Factory wheels — pick one as your current wheel:
Rim width in inches as stamped on the wheel (8J = 8″) · offset in mm (ET45 = 45; negative for deep-dish wheels)
Check the clearance
The outer edge sits 11 mm further out: check the fender clearance at full suspension compression and full steering lock.
| Measurement | Current | New | Diff |
|---|---|---|---|
| Rim width | 191 mm 7.50″ | 203 mm 8.00″ | +13 mm |
| Offset (ET) | 45 mm | 40 mm | −5 mm |
| Backspacing | 153 mm 6.02″ | 154 mm 6.07″ | +1 mm |
| Front spacing | 63 mm 2.48″ | 74 mm 2.93″ | +11 mm |
Backspacing: mounting face to the inner edge. Front spacing: mounting face to the outer edge. Both count half an inch for each rim flange.
Top view
How wheel offset works
Positive, zero and negative offset
With positive offset the mounting face sits outside the rim’s centre line, tucking the wheel in — almost every modern car. Zero offset puts it on the centre line. Negative offset puts it inside, pushing the wheel out: the deep-dish look of many truck and off-road wheels.
Width and offset together
A wheel 1″ wider at the same offset grows about 12.7 mm on each side. To keep the inner edge where it was, lower the offset by the same 12.7 mm — the extra width then all goes outward. This is why the calculator shows both edges, not only the offset.
The 5 mm rule
A new wheel that sits within about 5 mm of the original on both sides usually fits like stock. Between 5 and 15 mm, check the gap to the strut, spring and brake lines inside, and to the fender lip outside at full compression and full lock.
Look up your car’s factory wheel widths and offsets by make and model, its bolt pattern, or compare tire sizes for the new wheels in the tire size calculator.
Wheel offset FAQ
What is wheel offset?
Offset (ET, from the German Einpresstiefe) is the distance in millimetres from the centre line of the rim to the face that bolts to the hub. Positive offset puts that face toward the outside, so the wheel sits further in; negative offset pushes the wheel out. Most modern cars use positive offsets between ET30 and ET50.
How much can wheel offset change?
As a rule of thumb, a new wheel should sit within about 5 mm of the original on both the inside and the outside. Up to 15 mm can work after checking the clearance; beyond that it usually rubs the suspension or the fender. A wider wheel moves both edges at once, so check both numbers, not only the offset.
What is backspacing?
Backspacing is the distance from the mounting face to the inner edge of the wheel, in inches or millimetres. It decides how close the wheel gets to the suspension: more backspacing, less room. This calculator works it out from the width and offset, counting half an inch for each rim flange.
Does a lower offset make the wheel stick out?
Yes. Lowering the offset by 10 mm moves the whole wheel 10 mm outward: 10 mm more room on the inside, 10 mm more poke on the outside. A wider wheel at the same offset grows by half its extra width on each side.
What else must match besides the offset?
The bolt pattern (PCD) and the centre bore must suit the car, and the wheel must be rated for its load. The offset only decides where the wheel sits; check your car's bolt pattern and factory offsets on its page in our size database.