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Calculator Tools
Tire & Wheel Calculators

Wheel Offset Calculator

How changing wheel offset and width moves the wheel in or out of the arch.

Enter values

Results update as you type.

Result

Outer edge moves out by

22.7 mm

Inner edge moves in by
2.7 mm
Offset change
-10 mm
Width change
25.4 mm
Backspacing (original)
133.9 mm
Backspacing (new)
136.6 mm
Watch for
Arch clearance at the outer edge

About the Wheel Offset Calculator

How changing wheel offset and width moves the wheel in or out of the arch.

Also known as: et offset calculator, wheel spacer calculator, wheel fitment, offset change.

How to use this calculator

  1. Enter original wheel width, original offset, new wheel width, new offset.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

outer edge = width ÷ 2 − offset · inner edge = width ÷ 2 + offset

Worked example

Using the values pre-filled in the calculator above:

  • Original wheel width = 7 inches
  • Original offset = 45 mm ET
  • New wheel width = 8 inches
  • New offset = 35 mm ET

the calculator returns:

  • Outer edge moves out by: 22.7 mm
  • Inner edge moves in by: 2.7 mm
  • Offset change: -10 mm
  • Width change: 25.4 mm