Convert power and shaft speed into torque in newton-metres for motors, gearboxes and couplings.
Sizing the electrical supply for the same machine? Use the kVA to kW calculator.
Every diagram and table on this page updates with the calculator above.
The constant is 60,000 ÷ 2π.
Power equals torque multiplied by angular velocity: P = T × ω, with ω in radians per second.
ω = 2π × rpm ÷ 60, because one revolution is 2π radians and a minute is 60 seconds.
Multiplying by 1,000 and rearranging gives T = 9549.3 × kW ÷ rpm.
A 75 kW motor at 1,500 rpm produces about 477 N·m at its shaft — a useful anchor figure for four-pole motors on a 50 Hz supply.
At constant power, torque and speed trade off along a hyperbola. Halving the speed doubles the torque — which is precisely what a gearbox does, and why its output shaft is so much heavier than its input.
Your power rating at the synchronous speeds produced by 2-, 4-, 6- and 8-pole motors on 50 Hz and 60 Hz supplies.
| rpm | Torque (N·m) | Torque (lb·ft) |
|---|---|---|
| 375 rpm | 1,909.9 | 1,408.6 |
| 500 rpm | 1,432.4 | 1,056.5 |
| 600 rpm | 1,193.7 | 880.4 |
| 750 rpm | 954.93 | 704.32 |
| 900 rpm | 795.77 | 586.93 |
| 1,000 rpm | 716.2 | 528.24 |
| 1,200 rpm | 596.83 | 440.2 |
| 1,500 rpm | 477.46 | 352.16 |
| 1,800 rpm | 397.89 | 293.47 |
| 2,400 rpm | 298.42 | 220.1 |
| 3,000 rpm | 238.73 | 176.08 |
| 3,600 rpm | 198.94 | 146.73 |
The fastest way to see how a gearbox ratio changes the torque a coupling has to carry: pick your power row, then read across the speeds.
| kW | 500 rpm | 750 rpm | 1,000 rpm | 1,500 rpm | 3,000 rpm |
|---|---|---|---|---|---|
| 1.5 kW | 29 | 19 | 14 | 10 | 5 |
| 5.5 kW | 105 | 70 | 53 | 35 | 18 |
| 11 kW | 210 | 140 | 105 | 70 | 35 |
| 22 kW | 420 | 280 | 210 | 140 | 70 |
| 45 kW | 859 | 573 | 430 | 286 | 143 |
| 75 kW | 1,432 | 955 | 716 | 477 | 239 |
| 160 kW | 3,056 | 2,037 | 1,528 | 1,019 | 509 |
Gearboxes, couplings and shafts are rated in newton-metres, so torque — not power — is the selection criterion. Service factors then account for how brutal the duty actually is.
| Duty | Service factor | Examples |
|---|---|---|
| Uniform, 8 h/day | 1.0 – 1.25 | Centrifugal pumps, fans, belt conveyors |
| Moderate shock | 1.25 – 1.5 | Reciprocating pumps, mixers, hoists |
| Heavy shock | 1.5 – 2.0 | Crushers, presses, shakers |
| Continuous, 24 h/day | +0.25 on the above | Process plant running without pause |
| From | To | Multiply by |
|---|---|---|
| N·m | lb·ft | 0.73756 |
| lb·ft | N·m | 1.35582 |
| N·m | kgf·m | 0.10197 |
| N·m | in·lb | 8.8507 |
Torque and energy share dimensions but are not the same quantity. Torque is a vector moment; energy is a scalar. Keep the notation straight in calculations.
29 calculators built on the same maths as the tool above. Each one has its own inputs, interactive diagrams and worked examples.
Common questions about converting kw to nm.