Practical tools for measured work
Wheel Offset Calculator & Fitment Visualizer
Compare a current and proposed wheel/tyre setup and see exactly how the geometry changes.
Current setup
inches
inches
mm
section width, mm
sidewall %
Proposed setup
inches
inches
mm
section width, mm
sidewall %
How it works
Poke and backspacing are measured relative to the fixed hub mounting face. Poke = wheel width ÷ 2 − offset; backspacing = wheel width ÷ 2 + offset. A larger poke means the wheel face sits further outboard (toward the fender); a larger backspacing means the wheel barrel extends further inboard, toward suspension and brake components.
Overall tyre diameter = wheel diameter + 2 × sidewall height, where sidewall height = tyre section width × aspect ratio. Ground clearance change and speedometer error follow directly from the change in rolling radius.
Limitations
This is a geometric comparison only. It cannot know your vehicle's specific fender lip, suspension travel, steering-lock clearance, or brake caliper size - all of which also determine whether a setup physically fits. A setup that looks clear here can still rub. Always cross-check against vehicle-specific fitment data or a test fit.
FAQ
What does a positive offset change mean?
Why did my speedometer error come out positive?
Does a bigger diameter always raise the car?
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