About the Torque Calculator
What is the Torque Calculator?
This torque calculator finds shaft torque from a motor's power and speed, or the torque produced by a force on a lever or spanner.
Results are shown in newton-metres, kilogram-force metres and pound-force feet.
How to use the Torque Calculator
- From (sample: Power and speed (motor shaft))
- Power (kW) (sample: 7.5)
- Speed (rpm) (sample: 1,440)
- Force (N) (sample: 100)
- Lever Arm (m) (sample: 0.5)
- Press Calculate Torque (results also refresh as you type). The result card shows the Torque, along with In kgf·m, In lbf·ft and Power in HP.
Formula used
T (N·m) = P (kW) × 9,549 ÷ rpm; T = F × r
- 9,549 = 60,000 ÷ 2π
- F, r = force in newtons and lever arm in metres
Motor starting torque can be 1.5–2.5 times the rated torque.
Worked example
These are the sample values already filled in the calculator above, and the result it returns for them:
| Input | Sample value |
|---|---|
| From | Power and speed (motor shaft) |
| Power (kW) | 7.5 |
| Speed (rpm) | 1,440 |
| Force (N) | 100 |
| Lever Arm (m) | 0.5 |
| Result | Value |
|---|---|
| Torque | 49.736 N·m |
| In kgf·m | 5.072 kgf·m |
| In lbf·ft | 36.683 lbf·ft |
| Power in HP | 10.05 HP |
Tips for using the Torque Calculator
- Lower speed means higher torque for the same power – gearboxes trade speed for torque.
- Use a calibrated torque wrench for bolts.