Sidewall Height Difference Calculator
Compare the sidewall height of two tires. See how many millimeters and inches of sidewall you gain or lose with a new size or larger wheel.
Compare sidewall height changes.
Sidewall Height Difference Calculator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Sidewall Height Difference Calculator Works?
The Sidewall Height Difference Calculator works by computing each tire's sidewall height and subtracting the old value from the new value. The tool uses 3 steps.
Enter both sizes
Type the current and proposed width and aspect ratio.
Compute both sidewalls
The calculator multiplies each width by its aspect ratio.
Show the change
The calculator returns the change in mm, inches and percent, with a negative value for a lower-profile tire.
Sidewall Height Difference Calculator Formula
The Sidewall Height Difference Calculator formula is ΔSH = (W₂ × AR₂ − W₁ × AR₁) ÷ 100.
ΔSH = SH₂ − SH₁ΔSH% = ΔSH ÷ SH₁ × 100ΔRim_mm ÷ 2 ≈ −ΔSH (plus sizing)- SH₁, SH₂
- Sidewall height of current and new tire (mm)
- ΔRim_mm
- Rim diameter change in mm
Worked example
Going from 225/45 R17 (101.25 mm sidewall) to 225/35 R19 (78.75 mm sidewall) removes 22.5 mm (0.89 in), or 22.2%, of sidewall. The 2-inch larger rim adds 25.4 mm (1.0 in) of radius, so the overall diameter grows by 2.9 mm (0.11 in).
Sidewall Height Difference Calculator Conversion Table
The Sidewall Height Difference Calculator conversion table shows sidewall loss or gain for 6 plus-size, minus-size and profile changes.
| Size change | Old sidewall | New sidewall | Change | Change (%) |
|---|---|---|---|---|
| 225/45 R17 → 225/40 R18 | 101.2 mm | 90.0 mm | -11.2 mm (-0.44 in) | -11.1% |
| 225/45 R17 → 225/35 R19 | 101.2 mm | 78.8 mm | -22.5 mm (-0.89 in) | -22.2% |
| 205/55 R16 → 205/50 R17 | 112.8 mm | 102.5 mm | -10.2 mm (-0.40 in) | -9.1% |
| 265/70 R17 → 275/60 R20 | 185.5 mm | 165.0 mm | -20.5 mm (-0.81 in) | -11.1% |
| 245/40 R18 → 245/45 R18 | 98.0 mm | 110.2 mm | 12.2 mm (0.48 in) | +12.5% |
| 235/45 R18 → 235/55 R17 | 105.8 mm | 129.2 mm | 23.5 mm (0.93 in) | +22.2% |
What is Sidewall Height Difference Calculator?
A Sidewall Height Difference Calculator is a tool that measures how much taller or shorter the sidewall of a new tire is compared with the current tire. Plus sizing always shortens the sidewall. Minus sizing always lengthens the sidewall.
Every 1-inch increase in rim diameter needs about 12.7 mm (0.5 in) less sidewall to keep the same overall diameter.
A sidewall reduction of more than 20% changes ride quality, noise and pothole damage risk in a way most drivers feel on the first drive.
What are the uses of Sidewall Height Difference Calculator?
There are 4 main uses of the Sidewall Height Difference Calculator, including ride quality forecasts and wheel damage checks.
Ride quality forecasts
Estimate how much cushioning is lost with a lower-profile tire.
Wheel damage checks
Avoid sidewalls under 90 mm (3.5 in) on rough roads.
Plus-size verification
Confirm that sidewall loss balances the rim growth.
Winter wheel planning
Measure the extra sidewall gained by fitting a smaller winter wheel.
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