Wheel Offset & Backspacing Calculator
Convert between offset and backspacing, then compare a candidate wheel against your stock spec to see exactly how much further it pokes out — or tucks in — and how much your track width changes.
Quick convert
Know one, get the other. Width is the physical rim width in inches.
Stock vs. new fitment
Enter your stock wheel spec and the new wheel you're considering to see how much further out (or tucked in) it sits, and the resulting track-width change.
Stock wheel
New wheel
Backspacing
5.38" → 5.54"
Poke / tuck change
+34.0 mm
sticks out further
Track width change
+68.1 mm
both sides combined
This is geometry, not a fitment guarantee — it doesn't know about your fender lip, camber, suspension travel, or control-arm clearance. Use it to narrow down options, then confirm with a test fit or your wheel shop before you order.
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Offset vs. backspacing, in plain terms
Every wheel has a mounting face — where it bolts to the hub — sitting somewhere between its two lips. Offset measures that position relative to the wheel's true centerline, in millimeters. Backspacing measures the same position from the back (inboard) lip, in inches. They describe the same physical spot two different ways, which is why they convert directly:
backspacing (in) = width (in) / 2 + offset (mm) / 25.4
Why it matters for fitment
The hub face itself doesn't move — it's bolted to a fixed point on the car. What changes between wheels is how much material sits on each side of that fixed point. A lower offset shifts more of the wheel to the outboard side (poke, toward the fender), while a higher offset shifts more to the inboard side (toward struts, control arms, and brake calipers). Going wider affects both sides at once, which is why a wider-but-same-offset wheel can rub on the inside even if it clears the fender fine.
What this calculator doesn't know
It's pure geometry — width and offset in, poke and backspacing out. It has no idea about your fender lip, camber, suspension travel, or how close your control arms sit to the wheel. Use it to shortlist realistic offsets, then confirm with a test fit, a fitment thread for your exact car, or your wheel shop before you buy.
Frequently asked questions
- What is wheel offset?
- Wheel offset (ET) is the distance in millimeters between a wheel's true centerline and its hub mounting face. Positive offset moves the mounting face toward the outside (face) of the wheel, tucking it in. Negative offset moves it toward the inside, pushing the wheel out — more poke.
- How do I convert offset to backspacing?
- Backspacing (inches) = wheel width / 2 + offset (mm) / 25.4. An 8" wide wheel with +35mm offset works out to about 5.38" of backspacing.
- Does lower offset mean more poke?
- Yes. Lower or negative offset shifts the hub mounting face toward the inboard side of the wheel, which pushes the outboard face further from the car and increases poke. Higher positive offset tucks the wheel in.
- Is a wider wheel with the same offset safe to fit?
- Not automatically. Adding width with the same offset pushes material out on both the inboard and outboard sides, so it can poke past the fender and also close up clearance to struts or control arms on the inside — check both directions, not just the visible poke.