Wheel & tire calculator

Wheel Offset & Backspacing Calculator

Convert offset and backspacing or compare how two wheel widths and offsets change nominal inner and outer position.

Calculator Mode
Width Mode

Nominal width excludes flanges. Use measured overall width for the most accurate result.

Default 1.0 in combined. Only used in nominal mode.

Results are dimensional estimates. This calculator does not confirm wheel safety, vehicle compatibility, or clearance.

How offset and backspacing are calculated

Offset is the signed distance between the wheel centreline and the mounting face. Backspacing is the distance from the mounting face to the inner rim edge.

Formula: backspacing = overall wheel width ÷ 2 + offset ÷ 25.4. The reverse calculation is offset = (backspacing − overall width ÷ 2) × 25.4.

Nominal width versus measured width

The stamped wheel width is measured between bead seats and excludes the rim flanges. Nominal mode therefore adds a configurable flange allowance. For the most accurate backspacing result, measure the complete outside width of the wheel and use measured mode.