Rim Offset Calculator
Calculate the new rim offset and backspacing when changing wheel width or offset. Perfect for custom wheel fitment and tire clearance planning.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Rim Offset Calculator
- Enter Old Wheel Width (in inches) – e.g., 8.0
- Enter Old Offset (in mm) – e.g., 35
- Enter New Wheel Width (in inches) – e.g., 9.0
- Enter New Offset (in mm) – e.g., 25
- Click Calculate or press Enter.
What You Get:
- Backspacing (distance from mounting surface to inner rim edge) and Frontspacing (distance to outer rim edge) for both wheels.
- Change in clearance to suspension and fender: positive = more clearance (green), negative = less clearance (red).
Important: All widths are converted to mm (1 inch = 25.4 mm). Ensure inputs are positive numbers for widths; offsets can be negative.
Previous Results
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Frequently Asked Questions
Rim offset is the distance from the wheel's mounting surface to its centerline. Positive offset means the mounting surface is closer to the outside of the wheel (common in modern cars), negative offset means it's closer to the inside (deep dish look).
Backspacing is the distance from the mounting surface to the inner edge of the wheel. It determines how much space is available between the wheel and suspension components.
Positive clearance change means more space (better fit), negative means the wheel will be closer to the suspension or fender. Always double-check with physical measurements before purchasing new wheels.