Wheel Offset Calculator

This calculator works by measuring the distance from the wheel's center plane to the hub mounting face. Positive offset puts the mounting face toward the outside; negative offset puts it toward the inside.

1. Enter the wheel width, for example 8.0 in.
2. Enter the backspacing, for example 5.88 in.
3. Read the offset: +35 mm (+1.38 in).
4. Read the offset type: positive.

The formula is Offset = Backspacing − (Wheel Width ÷ 2 + 0.5 in), converted to millimeters.

The 0.5 in term covers the flange lip on the inner side. Worked example: a 9.0 in wheel with 5.0 in backspacing gives (5.0 − 4.5 − 0.5) × 25.4 = 0 mm, a zero offset.

The conversion table converts 12 offsets from −44 mm to +55 mm into inches, with the type and stamped ET marking. ET comes from the German "Einpresstiefe," meaning press-in depth.

Most front-wheel-drive cars use +35 to +55 mm. Lifted trucks often use 0 to −44 mm to push the wheel outward.

The Wheel Offset Calculator is a tool that finds the distance between a wheel's center line and its mounting face. Offset decides where the wheel sits in the wheel well.

Offset is stamped on most wheels as ET plus a number, for example ET40. Changing offset by 10 mm moves the whole wheel and tire 10 mm in or out.

This calculator has 4 uses: wheel shopping, fitment planning, stamp reading and backspacing conversion.

• Shop for wheels: Compare offsets across brands.
• Plan fitment: Position wheels for clearance and stance.
• Read wheel stamps: Turn ET markings into inches.
• Convert measurements: Turn measured backspacing into offset.