RPM Calculator
Ajax Loading🔧 Engine RPM ⓘ
Unit fixed to rpm.
⚙️ Transmission ratio ⓘ
No unit (dimensionless).
🛞 Wheel RPM ⓘ
Unit fixed to rpm.
⭕ Tire diameter ⓘ
Tip: 185/55R15 → ≈ 23 in overall diameter.
🚗 Vehicle speed ⓘ
mph ↔ km/h ↔ m/s ↔ ft/s conversions supported.
Quick summary
Auto-updates as you type. Enter any 3 fields to solve the rest.
Step-by-step derivation
References & constants
| Item | Value |
|---|---|
| π (pi) | 3.141592653589793 |
| Inches in a mile | 63,360 in |
| 1 mph | 1.609344 km/h = 0.44704 m/s = 1.4666667 ft/s |
| Inch conversions | 1 in = 25.4 mm = 2.54 cm = 0.0254 m = 1/12 ft |
| Core relations | RPMₑ = RPMᵥ × Ratio; Speed = RPMᵥ × D × π × 60 / 63360 |