Wheel Offset Calculator

Compare two wheel widths and offsets to estimate how far the inner and outer wheel edges move

This compares wheel-rim position only. Tire section width, suspension clearance and brake clearance must be checked separately.

Your result will appear here.

About the Wheel Offset Calculator

Wheel offset is the distance between a wheel’s mounting face and its centreline. It affects how far the wheel sits inward or outward in the wheel well and is important when comparing replacement wheels.

Offset alone does not determine clearance. Wheel width, tire size, suspension components, brakes and bodywork all influence whether a new wheel fits safely.

How to Use the Wheel Offset Calculator

  1. Enter the original wheel width and offset.
  2. Enter the new wheel width and offset.
  3. Calculate the change in inner and outer wheel position.
  4. Check tire and suspension clearance physically or against reliable fitment data before installation.

How the Calculation Works

Wheel centreline lies halfway across wheel width. Changing width moves both inner and outer edges relative to that centreline, while changing offset shifts the mounting face relative to the centre.

A common comparison converts wheel widths to millimetres, calculates half-width change and combines it with offset change to estimate additional inward and outward extension.

Worked example

Wheel Offset Calculator Worked Example

8-inch ET40 wheel to 9-inch ET35

The new wheel is 1 inch wider, or 25.4 mm, so half-width grows by 12.7 mm on each side. Offset drops by 5 mm, shifting the wheel outward. The outer edge therefore moves roughly 17.7 mm farther outward, while inner clearance changes by about 7.7 mm.

Result guide

Understanding Your Wheel Offset Calculator Result

The position change describes wheel rim geometry, not guaranteed tire clearance. Tire sidewall width and shape can extend beyond the rim.

Before you rely on the answer

Assumptions and Limitations

  • Wheel widths and offsets use the same mounting convention.
  • Widths are nominal rim widths appropriate for comparison.
  • Hub, brake, suspension and tire geometry are checked separately.

Practical tip

Using This Result in Practice

When changing both wheel width and offset, compare inner clearance and outer poke separately. Looking only at the offset number can hide a large width-driven change.

Related calculations

Useful Calculations to Continue With

If the tire dimensions are also changing, use the Tire Size Calculator to compare overall diameter and width.

If tire diameter changes materially, use the Speedometer Error Calculator to estimate the calibration effect.

Common questions

Wheel Offset Calculator FAQ

What does positive wheel offset mean?

The mounting face sits toward the wheel’s outer face relative to the centreline under the common convention.

Does lower offset push the wheel outward?

Generally yes, all else equal.

Can two wheels with the same offset fit differently?

Yes. Different widths change inner and outer positions even when offset is identical.