Sidewall Difference Calculator
See how the sidewall changes from one size to the next. Use the calculator below. Results update as you type.
Sidewall Height = Width × (Aspect Ratio / 100)How the Sidewall Difference Calculator Works
This calculator works by computing the sidewall height of 2 tires and subtracting one from the other. It shows the change in millimeters, inches and percent.
- Enter the current size, for example 205/55R16 (112.8 mm sidewall).
- Enter the new size, for example 225/45R17 (101.2 mm sidewall).
- Read the change: −11.5 mm (−0.45 in).
- Read the percentage: −10.2%.
A shorter sidewall means a firmer ride and sharper steering. A taller sidewall means more cushion and more flex.
The Formula
The formula is Sidewall Change = (W2 × AR2 ÷ 100) − (W1 × AR1 ÷ 100).
Sidewall_1 (mm) = W1 × AR1 ÷ 100 Sidewall_2 (mm) = W2 × AR2 ÷ 100 Change (%) = (Sidewall_2 − Sidewall_1) ÷ Sidewall_1 × 100 Sidewall Height = Width × (Aspect Ratio ÷ 100)Worked example for 275/65R18 to 285/75R18: 178.8 mm to 213.8 mm, a change of +35.0 mm (+1.38 in), or +19.6%.
Conversion Table
The conversion table compares sidewall height for 8 size changes. Changes range from −20.5 mm to +35.0 mm.
Plus-size swaps (larger rim) always cut the sidewall, by 8–19% in this table. All-terrain upsizes at the same rim add sidewall, by 8–20%.
| Tire 1 | Tire 2 | Sidewall 1 (mm / in) | Sidewall 2 (mm / in) | Change (mm) | Change (%) |
|---|---|---|---|---|---|
| 205/55R16 | 225/45R17 | 112.8 / 4.44 | 101.2 / 3.99 | -11.5 | -10.2% |
| 225/45R17 | 225/40R18 | 101.2 / 3.99 | 90.0 / 3.54 | -11.2 | -11.1% |
| 235/45R18 | 245/35R19 | 105.8 / 4.16 | 85.8 / 3.38 | -20.0 | -18.9% |
| 215/65R16 | 215/60R17 | 139.8 / 5.50 | 129.0 / 5.08 | -10.8 | -7.7% |
| 245/70R17 | 265/70R17 | 171.5 / 6.75 | 185.5 / 7.30 | +14.0 | +8.2% |
| 265/70R17 | 275/60R20 | 185.5 / 7.30 | 165.0 / 6.50 | -20.5 | -11.1% |
| 255/55R18 | 255/50R19 | 140.2 / 5.52 | 127.5 / 5.02 | -12.8 | -9.1% |
| 275/65R18 | 285/75R18 | 178.8 / 7.04 | 213.8 / 8.42 | +35.0 | +19.6% |
What Is the Sidewall Difference Calculator?
The Sidewall Difference Calculator is a tool that compares the sidewall heights of 2 tires. Sidewall height decides ride quality more than any other dimension.
The calculator isolates sidewall from overall diameter. Two sizes can share a diameter and still differ in sidewall by over 25 mm (1 in) when the rim size changes.
Common Uses
This calculator has 4 uses: comfort planning, steering feel, rim protection and air-down planning.
- Plan comfort: Predict a harsher or softer ride.
- Judge steering feel: Shorter sidewalls flex less in corners.
- Protect rims: Check pothole and curb exposure.
- Plan airing down: Taller sidewalls allow lower trail pressures.