Enter your Wheel Width and Offset (ET) to calculate your Backspace, or flip it around and enter your Backspace to find your Calculated Offset — the Wheel Offset Calculator also uses your Tire Width, Tire Profile, and Wheel Diameter to give you Total Diameter, Sidewall Height, and Frontspace.
Calculated Backspace
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Calculated Offset
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Total Diameter
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Sidewall Height
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Frontspace
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Wheel offset is the distance in millimeters from the centerline of the wheel to the mounting surface. Positive offset means the mounting surface is toward the front (outside) of the wheel, while negative offset means it's toward the back (inside).
Backspacing is the distance from the mounting surface to the back edge of the wheel rim, measured in inches. It determines how far the wheel sits inward toward the suspension and brake components.
To convert: Backspace = (Wheel Width ÷ 2) + (Offset ÷ 25.4). To find offset from backspacing: Offset = (Backspace - Wheel Width ÷ 2) × 25.4. The conversion accounts for the difference between inches and millimeters.
Changing offset affects wheel positioning relative to the fender and suspension. More positive offset moves the wheel inward (less poke), while more negative offset moves it outward (more poke). This impacts clearance, handling, and appearance.
Yes, but within reasonable limits. Small changes (±10-15mm) are usually safe, but larger changes may require modifications or cause clearance issues. Always check for adequate clearance from suspension, brakes, and fenders.
Backspace is the distance from the mounting surface to the back edge of the rim. Frontspace is the distance from the mounting surface to the front edge. Together, they equal the total wheel width plus rim thickness.
Tire width and sidewall height affect the total wheel package size. Wider tires may require more clearance, while lower profile tires reduce overall diameter. The calculator helps determine the complete wheel and tire dimensions.
Proper offset ensures adequate clearance from suspension components, brake calipers, and fenders. Incorrect offset can cause tire rub, affect steering geometry, put extra stress on bearings, and create safety hazards.