Tire Size Calculator
GoCalc
Enter a tire size code (e.g., 225/45R17) to calculate tire diameter, circumference, sidewall height, and revolutions per mile.Updated 2026-03-17
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R
Common Tire Sizes
| Tire Size | Diameter | Circumference | Revs/Mile |
|---|---|---|---|
| 195/65R15 | 634.5 mm (24.98″) | 1993.3 mm | 805 |
| 205/55R16 | 631.9 mm (24.88″) | 1985.1 mm | 808 |
| 215/60R16 | 664.2 mm (26.15″) | 2086.5 mm | 769 |
| 225/45R17 | 634.3 mm (24.97″) | 1992.6 mm | 805 |
| 225/50R17 | 656.8 mm (25.86″) | 2063.3 mm | 778 |
| 235/40R18 | 645.4 mm (25.41″) | 2027.4 mm | 792 |
| 245/45R18 | 678.1 mm (26.70″) | 2130.1 mm | 753 |
| 255/35R19 | 661.5 mm (26.04″) | 2078.0 mm | 772 |
| 265/35R20 | 693.5 mm (27.30″) | 2178.5 mm | 737 |
| 275/40R20 | 728.0 mm (28.66″) | 2286.9 mm | 702 |
How to Read a Tire Size Code
A tire size like 225/45R17 means:
- 225 — Tread width in millimeters
- 45 — Aspect ratio (sidewall height is 45% of the width)
- R — Radial construction
- 17 — Rim diameter in inches
Formulas:
- Sidewall height = Width × (Aspect Ratio / 100)
- Overall diameter = (2 × Sidewall) + (Rim × 25.4)
- Circumference = π × Diameter
- Revs per mile = 63,360 / (π × Diameter in inches)
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