RPM Calculator
Turn surface speed, road speed or power and torque into RPM, or RPM back into speed.
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RPM
- RPM
- Surface speed
- Rim speed
- Hertz
- Radians per second
- Per Second
Saved Speeds
Items you add are saved in this browser.
| Name | From | RPM | Ft./Min. | Remove |
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How to Calculate RPM
RPM is revolutions per minute. Each revolution moves a point on the rim one circumference, π × diameter, so speed and RPM convert through the circumference.
RPM = surface speed (ft/min) × 12 ÷ (π × diameter in inches) ≈ 3.82 × SFM ÷ D
Wheel RPM = mph × 5,280 × 12 ÷ 60 ÷ (π × tire diameter in inches) ≈ 336 × mph ÷ D
From power: RPM = hp × 5,252 ÷ torque (lb-ft)
Radians per second = RPM × 2π ÷ 60 Hz = RPM ÷ 60
Worked Example
Common Conversions
| RPM | Hz | rad/s | Surface ft/min on a 10″ wheel |
|---|
Tips
For machining, use the speeds and feeds calculator, which adds feed rate and chip load. For vehicle engine RPM at a given speed, the gear ratio and RPM at speed calculator includes the transmission and axle ratios. Grinding wheels and saw blades list a maximum safe RPM; never exceed it.