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Horsepower Calculator

Turn engine torque and rpm into kW, hp and PS, or find the torque behind a power figure.

By Nitin Raturi · Last reviewed

Your engine

How to use the Horsepower Calculator

Convert between engine torque and power at a given speed.

  1. Choose whether to find power or torque.
  2. Enter the torque or power you know and its unit.
  3. Enter the engine speed in rpm.
  4. Read the result in every common unit.

Good to know

  • Power = torque × angular speed, so the same torque gives more power at higher rpm.
  • In pound-feet and imperial horsepower, the two figures are equal at about 5,252 rpm.
Find

Find

Whether to work out power from torque, or torque from power.

How to fill it in

  • Choose Power to enter torque and rpm.
  • Choose Torque to enter power and rpm.

Torque or power

The figure you know, at the engine speed below.

How to fill it in

  • Read it from the specification sheet, for example “200 Nm @ 4,000 rpm”.
  • Enter 0.001 to 1,00,000 in the unit you choose.

Example

200 N·m at 6,000 rpm is 125.66 kW, or 170.86 PS.

Keep in mind: Peak torque and peak power usually occur at different speeds; use the rpm that goes with your figure.

Torque unit

Unit

The unit of the figure you entered.

How to fill it in

  • Torque: N·m (newton metres), lbf·ft (pound-feet) or kgf·m.
  • Power: kW, hp (imperial, 550 ft·lbf/s) or PS (metric horsepower, often written bhp in India).

Example

1 kW is 1.3410 hp or 1.3596 PS.

Engine speed

Revolutions per minute at which the torque or power is measured.

How to fill it in

  • Enter 1 to 30,000 rpm.

Example

A small motorcycle making 27 N·m at 4,000 rpm produces 11.31 kW there. 150 hp at 6,000 rpm needs 178.02 N·m.

Power

125.66 kW · 170.86 PS

200 N·m at 6,000 rpm is 125.66 kW, 168.52 hp or 170.86 PS.

Power
125.66 kW · 168.52 hp · 170.86 PS
Torque
200.00 N·m · 147.51 lbf·ft · 20.39 kgf·m
Angular speed
628.32 rad/s

Power = torque × angular speed (2π × rpm ÷ 60). hp is imperial horsepower (745.7 W); PS is metric horsepower (735.5 W). Figures are at the shaft; losses are not modelled.

ChangelogHow we test this calculatorEmbed this calculator

How this calculator works

  1. Step 1Speedω = 2π × rpm ÷ 60Turn rpm into radians per second.
  2. Step 2PowerP = T × ωTorque in N·m times ω gives watts.
  3. Step 3UnitskW, hp, PSDivide by each unit’s watts.

Torque is the twisting force an engine makes. Power is how fast it does work, which is torque multiplied by how fast the shaft turns.

The calculator works in newton metres and watts, then converts. Every unit factor is built from its legal definition, as listed by NIST.

Worked example: 200 N·m at 6,000 rpm

Power from torque
ω
2π × rpm ÷ 60
P
T × ω
  1. Angular speed2π × 6,000 ÷ 60628.32 rad/s
  2. Power200 × 628.321,25,663.71 W
  3. Kilowatts÷ 1,000125.66 kW
  4. Imperial hp÷ 745.7168.52 hp
  5. Metric hp (PS)÷ 735.5170.86 PS

The same engine quoted in PS shows a slightly larger number than in hp, because a metric horsepower is about 1.4% smaller.

Read the result

  • kW1
  • hp (imperial)1.3410
  • PS (metric)1.3596
One kilowatt in each unit

In pound-feet and imperial horsepower, the two numbers cross near 5,252 rpm: 100 lbf·ft there is 100.00 hp.

Torque from power

  • 150 hp at 6,000 rpm178.02 N·mOr 131.30 lbf·ft of torque at that speed.
  • 27 N·m at 4,000 rpm11.31 kWA small motorcycle figure: 15.38 PS.

Assumptions and limits

  • Same speedTorque and power are at the rpm you enter.
  • Shaft figuresGearbox and tyre losses are not included.
  • Exact factorshp = 550 ft·lbf/s; PS = 75 kgf·m/s.
  • Not a dynoIt converts figures; it cannot measure an engine.

Power is the rate of doing work. Speed, energy and fuel use follow from it.

For the energy of a moving vehicle, use the kinetic energy calculator. To compare tyre sizes and speedometer error, try the tyre size calculator, and for fuel economy, the gas mileage calculator.

Common mistakes

  • Mistake: Combining peak torque with peak-power rpm.

    Instead: Use the torque at the same rpm as the power.

  • Mistake: Treating PS and hp as the same.

    Instead: 1 PS is about 0.986 hp.

  • Mistake: Reading kgf·m as N·m.

    Instead: 1 kgf·m is 9.80665 N·m.

Checking the method

A separate script re-works every golden value from the 33,000 ft·lbf per minute definition and NIST’s printed factors, without radians.

Read how we test our calculators, or browse more everyday tools.

Frequently asked questions

How much power is 200 N·m at 6,000 rpm?

125.66 kW, which is 168.52 hp or 170.86 PS.

What is the difference between hp, bhp and PS?

hp is imperial horsepower, 550 ft·lbf/s (745.7 W). PS is metric horsepower, 75 kgf·m/s (735.5 W). bhp means power at the crankshaft and is quoted in either; 1 kW is 1.3410 hp or 1.3596 PS.

How much torque does 150 hp at 6,000 rpm need?

178.02 N·m, or 131.30 lbf·ft.

Why do torque and horsepower curves cross at 5,252 rpm?

Because hp = lbf·ft × rpm ÷ 5,252. At 5,252 rpm, 100 lbf·ft gives 100.00 hp.

Does this include gearbox losses?

No. It converts figures at the same shaft; power at the wheels is lower.

Sources and methodology

The formulas are standard time-value-of-money results. We check every figure against golden values worked out independently, by closed form and by month-by-month simulation; see the methodology.

Written and maintained by Nitin Raturi, a software engineer (about the author). Last reviewed 4 Nov 2026; next review due by . Found an error? Tell us.

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