Tire Height Difference Calculator
See how much taller or shorter a new tire is. Use the calculator below. Results update as you type.
How the Tire Height Difference Calculator Works
This calculator works by subtracting the old overall diameter from the new one and reporting the gap in inches, millimeters and percent. It focuses on height only.
- Enter the current size, for example 245/70R17.
- Enter the new size, for example 265/70R17.
- Read the height difference: +1.10 in (+28.0 mm).
- Read the percentage: +3.61%.
The ground clearance change is half the height difference: 0.55 in (14 mm) in this example.
The Formula
The formula is Height Difference = New Diameter − Old Diameter. The percentage version divides by the old diameter.
Height Difference (in) = D_new − D_old Height Difference (%) = (D_new − D_old) ÷ D_old × 100 Clearance Change = Height Difference ÷ 2Worked example for 225/50R17 to 225/55R17: D_old = 25.86 in, D_new = 26.74 in, difference = +0.89 in (+22.5 mm), or +3.43%.
Conversion Table
The conversion table shows the height difference for 8 size pairs in inches, millimeters and percent. Gaps range from +0.47 in (+12.0 mm) to +1.65 in (+42.0 mm).
A 10 mm width increase at a 65 series adds 0.51 in, and a 20 mm increase at a 70 series adds 1.10 in. A 5-point aspect increase on a 225 mm tire adds 0.89 in.
| Tire 1 | Tire 2 | Difference (in) | Difference (mm) | Difference (%) |
|---|---|---|---|---|
| 195/65R15 | 205/65R15 | +0.51 | +13.0 | +2.05% |
| 205/60R16 | 215/60R16 | +0.47 | +12.0 | +1.84% |
| 225/50R17 | 225/55R17 | +0.89 | +22.5 | +3.43% |
| 235/60R18 | 255/60R18 | +0.94 | +24.0 | +3.25% |
| 245/70R17 | 265/70R17 | +1.10 | +28.0 | +3.61% |
| 265/65R18 | 275/70R18 | +1.59 | +40.5 | +5.05% |
| 275/60R20 | 285/65R20 | +1.59 | +40.5 | +4.83% |
| 285/70R17 | 315/70R17 | +1.65 | +42.0 | +5.06% |
What Is the Tire Height Difference Calculator?
The Tire Height Difference Calculator is a tool that measures how much taller or shorter a new tire is than the current tire. Height difference is the single number that predicts speedometer error, ground clearance change and fender clearance loss.
The calculator reports the change in 3 forms. Inches suit lift-kit planning, millimeters suit European data sheets, and percent suits the ±3% fitment rule.
Common Uses
This calculator has 4 uses: clearance planning, fender checks, speedometer prediction and lift matching.
- Plan ground clearance: Halve the height change to find axle lift.
- Check fenders: Compare the change with measured fender gap.
- Predict speedometer error: Use the percentage directly as the error.
- Match lifts: Size tires to the height a lift creates.