Wheel Offset Calculator
Compare wheel widths and offsets to calculate inner and outer position changes in millimeters and nominal backspacing in inches.
Backspacing is nominal and excludes the rim flange. Clearance change is relative to your current wheel; measure vehicle clearance separately.
About the Wheel Offset Calculator
Use this wheel offset calculator to compare a proposed wheel with your current wheel. Enter both widths in inches and offsets in millimeters. The result shows how far the outer edge moves outward and the inner edge moves inward, plus nominal backspacing calculated from the supplied width. For example, changing from 7 to 8 inches at the same offset adds 12.7 mm on each side. Outer clearance change is relative to the current wheel, not a measurement of available fender clearance. Tire shape, suspension, bodywork and rim flanges are not measured by this tool.
Features
- Outer and inner position changes in millimeters
- Nominal backspacing in inches, excluding rim flange
- Relative outer clearance change
- Comparison of current and proposed widths and offsets
- Local calculation and copy
How to use this tool
The Wheel Offset Calculator works right in your browser — no signup, no installation. Follow these steps:
- Enter current width in inches and offset in millimeters.
- Enter proposed width and offset.
- Compare positive outward and inward changes.
- Measure actual vehicle and tire clearance separately before selecting wheels.
Frequently asked questions
Why does adding one inch of width add 12.7 mm per side?
At the same offset, the extra 25.4 mm is divided equally around the centerline.
How is nominal backspacing calculated?
Half the entered wheel width in inches plus the offset in millimeters divided by 25.4. The displayed nominal value excludes any rim flange allowance.
Can this confirm that wheels will fit without rubbing?
No. It compares wheel positions only. It does not know the available clearance, tire dimensions, suspension movement or bodywork.
Using the results
The Wheel Offset Calculator estimates quantities from your measurements and the stated assumptions. Check dimensions, product coverage and project requirements before buying materials.