Wheel Offset Calculator

How to use Wheel Offset Calculator

1. Enter your figures in the units shown beside each field. Keep monetary inputs in the same currency; money results are currently displayed in USD.
2. Select the unit standard where the form offers a choice, then choose Calculate.
3. Read the breakdown and compare the worked example below. Change one assumption to see its effect.

Formula used

Outer extension = (new width − old width)/2 − (new offset − old offset), with widths converted to mm. Inner clearance change is the negative of the half-width change plus offset change.

Worked example

From 7.5 inches ET45 to 8.5 inches ET40, the outer edge extends 17.7 mm farther out and inner clearance decreases by 7.7 mm.

What the result means

This compares wheel geometry only. Tyre bulge, spokes, brakes, suspension travel and body clearance still need checking.

Check your result

Results retain calculation precision internally and round for display. Keep the input values with the result so you can reproduce it. Use Reset to restore the example inputs, or Copy result to copy the displayed answer.

If the result does not agree with your own calculation, report the page, inputs and expected answer. See our methodology and reference sources for the standards used.

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