Horsepower equals torque in lb-ft times rpm divided by 5,252. So 300 lb-ft at 5,252 rpm is 300 hp, and 300 lb-ft at 4,000 rpm is about 228 hp. In metric, power in watts is torque in N·m times 2π times rpm ÷ 60; divide by 745.7 for hp.
Torque alone does not tell you how much work an engine does; you need the speed it turns at. Tuners reading a dyno sheet, students checking a mechanics problem and buyers comparing spec tables quoted in N·m and kW all hit the same conversion. Enter the torque, pick lb-ft or N·m in the field, and the engine speed. The result shows mechanical horsepower, kilowatts, metric PS and the torque in both units, with the working written out. One limit: the figure is power at that single rpm. Peak torque and peak power occur at different speeds, so multiplying peak torque by redline does not give peak horsepower.
Type the torque value read at one engine speed.
Use the unit selector inside the torque field.
Give the rpm at which that torque was measured.
Horsepower, kW and PS update as you type, with the steps below.
Result Horsepower (mechanical hp): 300.0
Kilowatts: 223.71
Metric horsepower (PS): 304.2
Torque in lb-ft: 300
Torque in N·m: 406.7
At 5,252 rpm the torque and horsepower figures are the same number, which is why dyno curves cross there.
Result Horsepower (mechanical hp): 42.1
Kilowatts: 31.42
Metric horsepower (PS): 42.7
Torque in lb-ft: 73.8
Torque in N·m: 100
A small petrol engine's mid-range: 31.4 kW, or about 42 hp at the crank.
Result Horsepower (mechanical hp): 337.0
Kilowatts: 251.33
Metric horsepower (PS): 341.7
Torque in lb-ft: 295
Torque in N·m: 400
A sporty turbo four near its power peak: about 251 kW, or 337 hp.
P (W) = T (N·m) × 2π × N ÷ 60; hp = P ÷ 745.7 = T (lb-ft) × N ÷ 5252
TNPPower is torque multiplied by angular speed in radians per second, which is rpm × 2π ÷ 60. Watts are divided by 745.69987 to get mechanical horsepower (550 ft·lbf/s) and by 735.49875 for metric PS. With torque in lb-ft the constants collapse to 33,000 ÷ 2π ≈ 5,252, giving the shop formula. Lb-ft converts to N·m by the NIST factor 1.3558179.
One horsepower is 33,000 ft·lbf per minute, and one revolution sweeps 2π radians. Dividing 33,000 by 2π gives 5,252.1, so at that speed the lb-ft number and the hp number are identical. Below it torque reads higher; above it horsepower reads higher. In N·m and kW there is no such crossing at that speed.
Mechanical horsepower is 745.7 W, metric horsepower (PS, CV, PK) is 735.5 W, and a kilowatt is 1,000 W. European spec sheets often quote PS and kW, US ones hp. A 100 kW engine is 134.1 hp or 136.0 PS.
No. Power is the rate of doing work, and torque is a twisting force. The same 300 lb-ft gives 57 hp at 1,000 rpm and 343 hp at 6,000 rpm. You need the speed at which the torque was measured.
It gives power at whatever shaft the torque was measured on. Manufacturer figures are usually crank values; a chassis dyno measures at the wheels, typically 10 to 20 percent lower because of gearbox and differential losses.
Rearrange the formula: torque in lb-ft equals hp × 5,252 ÷ rpm. For example, 200 hp at 4,000 rpm is 262.6 lb-ft, or 356.1 N·m.
Yes, the physics is the same for any rotating shaft. Enter the motor torque and the shaft speed at that operating point. Note that motor datasheets distinguish continuous and short-term peak ratings, so use matching figures.
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 to Horsepower. Tools Directory. Retrieved October 28, 2026, from https://tools.milunir.com/automotive/engine-and-performance/torque-to-horsepower/
Tools Directory Editorial Team. “Torque to Horsepower.” Tools Directory, 13 Oct. 2026, https://tools.milunir.com/automotive/engine-and-performance/torque-to-horsepower/. Accessed 28 Oct. 2026.
Tools Directory Editorial Team. “Torque to Horsepower.” Tools Directory. Last modified October 13, 2026. Accessed October 28, 2026. https://tools.milunir.com/automotive/engine-and-performance/torque-to-horsepower/.
<a href="https://tools.milunir.com/automotive/engine-and-performance/torque-to-horsepower/">Torque to Horsepower – Tools Directory</a>