Professional wheel offset and backspacing calculator. Calculate ET values, track width changes, and ensure proper wheel clearance for safe fitment.
Red line shows offset position from wheel centerline
| Measurement | Original Wheel | New Wheel | Difference | Impact |
|---|
Wheel offset (ET) is the distance from the wheel's mounting surface to its centerline, measured in millimeters. It determines how far in or out the wheel sits relative to the hub.
Backspacing: Distance from mounting surface to inner wheel edge.
Formula: Backspacing = (Wheel Width ÷ 2) + Offset
Example: 8" wheel with ET35 offset
Backspacing = (8" ÷ 2) + 35mm = 4" + 1.38" = 5.38"
Now calculate the perfect tire size for your new wheels with our tire size calculator.