ac AutomotiveCalc
Tires & wheels

Wheel Offset Calculator

Compare wheel width and offset to estimate inner clearance and outward position changes, with a shared-scale diagram.

By AutomotiveCalc · Published September 9, 2026 · Method & standards

Your numbers

Example calculation

Example results are shown below. Controls become available when the calculator loads.

Use wheel width, not tire section width. Enter positive or negative offset in millimeters. Positive clearance change means more room inside; positive outer-position change means farther outward.

Inner clearance change-12.7 mm
Outer position change12.7 mm
Wheel width change25.4 mm
Wheel width and offset comparisonBoth widths share the same scale and hub mounting plane. Left is inboard, right is outboard. Nominal widths only; tires and wheel flanges are not shown.Original wheelNew wheel← InboardOutboard →
Dashed line: hub mounting plane. Nominal wheel widths at the same scale; flanges, spokes, and tires are excluded.

Inner clearance: 12.70 mm less estimated clearance.

Outer position: 12.70 mm farther outward.

Calculated on your device. No account needed. Report a problem

How to use this calculator

Replace the example values with your own measurements or specifications. Keep the units shown beside each label. Results update as you type; reset restores the example.

This is a relative geometry estimate with an unchanged hub mounting plane. Nominal wheel widths exclude the flange profile, so comparing physical lip positions assumes comparable flange dimensions. The tool does not calculate measured backspacing, tire bulge, brake-spoke clearance, steering travel, suspension movement, bolt pattern, load rating, or safe fitment. Confirm the full wheel and tire specification with the vehicle/wheel manufacturer or a qualified installer.

The formula

Convert width to mm: W = inches × 25.4. Inner reference = W ÷ 2 + offset. Outer reference = W ÷ 2 − offset. Clearance change = old inner − new inner. Outward change = new outer − old outer.

A worked example

Changing from an 8-inch wheel at +35 mm offset to a 9-inch wheel at +35 mm adds 25.40 mm of width. Half extends each way: estimated inner clearance decreases by 12.70 mm and the outer position moves outward by 12.70 mm. If only offset changes from +35 to +45 mm, both sides move 10 mm inward.

Common questions

What does positive offset mean?

The mounting face lies toward the outside face from the wheel centerline. For an unchanged width, a more positive offset moves the wheel inward. Negative offset places the mounting face on the inboard side of the centerline.

Why does a wider wheel reduce inner clearance?

At the same offset, the added width is split evenly between the inside and outside. A one-inch increase adds 12.70 mm to each side of this nominal-width model.

Does a positive clearance result mean the wheel fits?

No. It only describes the change in the inner reference position. The calculator has no existing clearance measurement or vehicle-specific fitment data. A wheel can still interfere with brakes, suspension, bodywork, or tires.

Is this a backspacing calculator?

No. Backspacing is measured to the inside wheel lip. This tool compares positions using the entered nominal widths and offsets; it does not assume an extra inch for wheel flanges or report a physical backspacing measurement.

Does wheel diameter affect this calculation?

Diameter does not enter this lateral-position model. It still matters for tire compatibility, brake clearance, and overall fitment. Use the tire-size tools for nominal tire diameter.

Sources & calculation method

Related guidance: Tire Rack: wheel offset and backspacing. Accessed September 9, 2026. The equation above describes this tool’s model; the reference provides practical context and does not endorse this site.

Prepared with AI assistance. Formula examples and input validation have automated checks. This page has not received an independent automotive professional review. Read our review standards.