Example
For the same 8-inch rim, changing ET from 35 to 45 moves the wheel centerline 10 mm inward: the inner edge moves 10 mm inward and the outer edge 10 mm inward.
How the comparison works
The calculator converts inputs to millimetres, compares the rim edges and wheel centerline, and draws a simple side-by-side geometry diagram. Optional remaining-clearance values are arithmetic estimates based only on the clearances you measured.
Frequently asked questions
What does a higher ET number do?
With the same rim width and spacer, a 10 mm higher ET moves the wheel centerline and both rim edges 10 mm inward.
How does a spacer affect effective ET?
A spacer moves the wheel outward, so the effective offset is ET minus spacer thickness. A 10 mm spacer changes effective ET by −10 mm.
Can this confirm that wheels fit my car?
No. It compares basic rim geometry only. It does not model the vehicle, tire shape, suspension, brakes, steering or legal approval.
What does remaining clearance mean?
If you enter measured current clearance, the calculator subtracts the estimated rim movement toward that side. Tire bulge and other parts are not included.
Are inches and millimetres supported?
Yes. Choose a unit for rim width and another for ET/spacers; results are displayed in millimetres.
Important limits
This is a geometry comparison, not a vehicle compatibility, safety, legal or homologation check. It cannot account for suspension shape, steering lock, tire bulge, brake clearance, manufacturing tolerances or loaded movement. Measure your vehicle and confirm fitment with a qualified professional before driving.