Torque equals power divided by rotational speed. In US units, torque (lb-ft) = horsepower × 5252 ÷ rpm; in SI, torque (N·m) = watts ÷ (2π × rpm ÷ 60). An engine making 200 hp at 6,000 rpm therefore produces about 175.1 lb-ft, or 237.4 N·m, at that speed.
Spec sheets often list peak power and peak torque at different engine speeds, and dyno sheets give power at many points. This calculator turns any power figure and the rpm it was measured at into the torque the crankshaft delivers at that same speed. Enter power in mechanical horsepower, kilowatts or metric PS, add the engine speed, and the result shows torque in lb-ft, newton-metres and kgf·m, plus the power in both hp and kW and the crank's angular speed in radians per second. It is handy for checking a manufacturer's figures, reading a dyno chart or comparing an electric motor with a petrol engine. One limit: the answer is the torque at that single rpm only; it cannot tell you the peak torque, which usually occurs lower in the rev range.
Type the power figure and pick hp, kW or PS from the unit menu inside the field.
Use the rpm at which that power was measured, for example the peak-power rpm from the spec sheet.
Torque in lb-ft is the headline; N·m, kgf·m and the converted power appear below with the working.
Result Torque: 300.0
Torque (N·m): 406.8
Torque (kgf·m): 41.48
Power (hp): 300
Power (kW): 223.7
Crank speed (rad/s): 550
At 5,252 rpm the hp and lb-ft figures are always equal, which is why dyno charts show the two curves crossing there.
Result Torque: 234.8
Torque (N·m): 318.3
Torque (kgf·m): 32.46
Power (hp): 134.1
Power (kW): 100
Crank speed (rad/s): 314.2
A typical turbo-diesel peak: 100,000 W divided by 314.16 rad/s gives 318.3 N·m, or 234.8 lb-ft.
Result Torque: 175.1
Torque (N·m): 237.4
Torque (kgf·m): 24.2
Power (hp): 200
Power (kW): 149.1
Crank speed (rad/s): 628.3
A rev-happy four-cylinder: 200 × 5252 ÷ 6000 is about 175 lb-ft at the power peak.
T = P ÷ ω, where ω = 2π × rpm ÷ 60; in US units T (lb-ft) = hp × 5252.113 ÷ rpm
TPωrpmPower is torque multiplied by angular speed. The tool converts the power to watts, the rpm to radians per second, divides to get newton-metres, then divides by 1.35582 to give lb-ft and by 9.80665 for kgf·m. The constant 5252 comes from 33,000 ft·lbf/min per horsepower divided by 2π.
Horsepower is defined as 33,000 ft·lbf per minute. Dividing that by 2π radians per revolution gives 5252.113, so hp = lb-ft × rpm ÷ 5252. At exactly 5252 rpm the two numbers are equal, which is why every dyno chart plotted in hp and lb-ft shows the curves meeting there.
Mechanical horsepower is 745.7 W. Metric horsepower, written PS or CV, is 735.5 W, about 1.4% less. European and Japanese specs often use PS or kW, so pick the matching unit before reading the torque.
Not reliably. Peak torque usually arrives well below the peak-power rpm, and the shape of the curve depends on the engine. This calculator gives the torque at the rpm you enter, so with the peak-power rpm you get the torque at that point, which is lower than the peak.
Multiply by 1.35582. For example, 300 lb-ft is 406.7 N·m. The result panel shows both figures, along with kgf·m, which some Japanese manuals still quote.
Yes. The relation between power, torque and speed is the same for any rotating shaft. Enter the motor's kW rating and the rpm at which it is delivered; note that many electric motors hold constant torque from zero up to a base speed, so peak torque is easier to read from the motor's data sheet.
Brochures quote peak torque, often at a different rpm from peak power, and may use DIN, SAE or ECE test standards that differ slightly. Use the rpm that matches the power figure you entered to compare like with like.
Using this tool in an assignment, article or report? Copy a citation, or a link for your website.
Tools Directory Editorial Team. (2026, October 13). Torque Calculator. Tools Directory. Retrieved October 28, 2026, from https://tools.milunir.com/automotive/engine-and-performance/torque-calculator/
Tools Directory Editorial Team. “Torque Calculator.” Tools Directory, 13 Oct. 2026, https://tools.milunir.com/automotive/engine-and-performance/torque-calculator/. Accessed 28 Oct. 2026.
Tools Directory Editorial Team. “Torque Calculator.” Tools Directory. Last modified October 13, 2026. Accessed October 28, 2026. https://tools.milunir.com/automotive/engine-and-performance/torque-calculator/.
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