Online Tool Store
Wheel Offset Calculator
Compare a new wheel's offset and width against your current setup to see how far the face and inner edge move, before anything is ordered.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Unit & Converters
Wheel Offset Calculator
Frontend preview — no upload or external service.
Fitment change
Going from 8.5J ET35 to 9.5J ET25 pushes the outer edge 22.7 mm further out and the inner edge 2.7 mm further in — arch clearance is the constraint, not the strut.
How the Wheel Offset Calculator works
- Enter your current wheel width and offset, using J width in inches and ET in millimetres.
- Enter the proposed wheel's figures.
- Read both the outer and inner movement — a wider wheel moves both edges, and the inner one is what hits suspension components.
The method
Offset is the distance from the wheel's mounting face to its centreline, so changing width moves both edges by half the width change, and changing offset moves the whole wheel.
inner change = (Δwidth / 2) + (ET_new - ET_old); outer change = (Δwidth / 2) - (ET_new - ET_old)
From 8.5J ET35 to 9.5J ET25: half an inch is 12.7 mm each side, and 10 mm less offset pushes everything out — so 22.7 mm out at the face, 2.7 mm in at the back.
FAQ
Does a lower ET always mean more poke?
Yes, for the same width — lower offset moves the wheel outboard. But width changes both edges at once, so a wider wheel with the same ET pokes and moves inboard simultaneously.
Does tyre width matter for clearance?
Very much. Tyre section width exceeds the rim width and bulges under load, so the tyre usually contacts an arch or a strut before the rim does.
Can spacers fix a fitment problem?
They move the wheel outboard only, which cures inner clearance and worsens the outer. They also need correct-length bolts and hub-centric design; this is a safety-critical part.
How we compare
| Feature | Online Tool Store | A search-engine answer box | A reference table |
|---|---|---|---|
| Inner and outer movement | ✓ | Manual | ✓ |
| Accounts for width change | ✓ | Manual | Yes |
| Free and account-free | ✓ | ✓ | ✗ |
| Guarantees fitment | ✗ | ✗ | ✗ |
Wheel Offset Calculator shows both edges moving, because the inner clearance against suspension is what fitment plans usually overlook.