Wheel & Tire Fitment Calculator | Fancy Craft |inset matching

Planning new wheels or spacers?
This tool shows how your setup affects tire clearance, offset, fitment, and speedometer accuracy — all visualized before and after.


Size（inch）	Rim width	Offset（mm）

Width（mm）	Aspect ratio（%）		Spacer thickness（mm）


Wheel size（inch）	Rim width	Offset（mm）

Width（mm）	Aspect ratio（%）		Spacer thickness（mm）

Fender Position Adjustment

mm outward from outer edge.
mm upward from the outer edge.

Change in wheel position
Outside	mm
Inside	mm

Speedometer error
%	Actual speed km/h when the speedometer reads 100 km/h (or mph).
Current tire: Outer diameter mm Circumference mm
Replaced tire: Outer diameter mm Circumference mm

This page was first published on March 28, 2015 as an upgrade from a script that calculated offset changes numerically, back when this site was called “SR GARAGE.”
Inspired by feedback like “It’s hard to understand the direction of change from numbers alone,” and the growing support for the <canvas> tag, I developed this visualized calculation system from the ground up.
The visualization method is entirely my original concept. Even if similar tools exist now, they all followed this concept.