About the RPM Calculator
What is the RPM Calculator?
This rpm calculator covers three everyday cases: the speed of a driven pulley or sprocket, the speed of an AC induction motor from its poles and supply frequency, and wheel rpm from road speed.
On India's 50 Hz supply, a 4-pole motor runs at about 1,440–1,460 rpm after slip.
How to use the RPM Calculator
- From (sample: Pulleys or sprockets)
- Driver Speed (rpm) (sample: 1,440)
- Driver Pulley Diameter or Teeth (sample: 100)
- Driven Pulley Diameter or Teeth (sample: 200)
- Supply Frequency (Hz) (sample: 50)
- Motor Poles (sample: 4 poles)
- Slip (%) (sample: 3)
- Linear Speed (km/h) (sample: 36)
- Wheel Diameter (mm) (sample: 600)
- Press Calculate RPM (results also refresh as you type). The result card shows the Speed, along with Speed ratio and Belt speed (if diameters in mm).
Formula used
Driven rpm = Driver rpm × Driver diameter ÷ Driven diameter
- Motor synchronous speed = 120 × f ÷ poles
- Wheel rpm = speed (m/s) ÷ (π × diameter) × 60
Belt slip reduces driven speed by 1–3% in practice.
Worked example
These are the sample values already filled in the calculator above, and the result it returns for them:
| Input | Sample value |
|---|---|
| From | Pulleys or sprockets |
| Driver Speed (rpm) | 1,440 |
| Driver Pulley Diameter or Teeth | 100 |
| Driven Pulley Diameter or Teeth | 200 |
| Supply Frequency (Hz) | 50 |
| Motor Poles | 4 poles |
| Slip (%) | 3 |
| Linear Speed (km/h) | 36 |
| Result | Value |
|---|---|
| Speed | 720 rpm |
| Speed ratio | 2 : 1 |
| Belt speed (if diameters in mm) | 7.54 m/s |
Tips for using the RPM Calculator
- Use teeth counts instead of diameters for gears and sprockets.
- Induction motor slip is typically 2–5% at full load.