Torque to kW Calculator
Convert torque in newton-meters and RPM into kilowatts instantly.
This calculator converts torque in newton-meters and engine speed in RPM directly into power in kilowatts — the metric equivalent of the 5252 horsepower rule.
Torque to kW Formula
The constant 9549 comes from converting radians per second and newton-meters into watts (it equals 60 × 1000 ÷ 2π). If your torque is in pound-feet, convert first (1 lb-ft = 1.3558 Nm) or use the imperial torque to HP calculator.
How to Use This Calculator
- Enter torque in newton-meters.
- Enter engine speed in RPM.
- Read kilowatts instantly, with the horsepower equivalent shown below.
Worked Example
The Metric Power Equation Explained
Where the imperial world uses HP = (lb-ft × RPM) ÷ 5252, the metric system uses kW = (Nm × RPM) ÷ 9549. Both express the same physics — power equals torque times angular velocity. The 9549 constant converts RPM to radians per second (×2π÷60) and newton-meters to kilowatts (÷1000). Knowing both lets you move freely between a European dyno sheet in Nm/kW and a US one in lb-ft/HP.
When to Use Torque-to-kW
This is the go-to conversion for engineers and EV enthusiasts working in SI units, or anyone reading a European engine spec. Electric motors in particular are characterised by their torque-and-speed curve, so converting a stated torque at a given RPM into kilowatts gives the power figure directly comparable to a battery or charger rating.
Nm to kW Chart Across the Rev Range
The same torque produces very different power depending on how fast the shaft is turning. Find your torque down the left and the engine speed across the top.
| Torque | 1,000 rpm | 2,000 rpm | 3,000 rpm | 4,000 rpm | 5,000 rpm | 6,000 rpm |
|---|---|---|---|---|---|---|
| 100 Nm | 10.5 | 20.9 | 31.4 | 41.9 | 52.4 | 62.8 |
| 150 Nm | 15.7 | 31.4 | 47.1 | 62.8 | 78.5 | 94.2 |
| 200 Nm | 20.9 | 41.9 | 62.8 | 83.8 | 104.7 | 125.7 |
| 250 Nm | 26.2 | 52.4 | 78.5 | 104.7 | 130.9 | 157.1 |
| 300 Nm | 31.4 | 62.8 | 94.2 | 125.7 | 157.1 | 188.5 |
| 350 Nm | 36.7 | 73.3 | 110.0 | 146.6 | 183.3 | 219.9 |
| 400 Nm | 41.9 | 83.8 | 125.7 | 167.6 | 209.4 | 251.3 |
| 500 Nm | 52.4 | 104.7 | 157.1 | 209.4 | 261.8 | 314.2 |
| 600 Nm | 62.8 | 125.7 | 188.5 | 251.3 | 314.2 | 377.0 |
| 800 Nm | 83.8 | 167.6 | 251.3 | 335.1 | 418.9 | 502.7 |
The Mistake That Ruins This Calculation
By far the most common error is pairing peak torque with peak-power rpm. They do not happen together.
Take a typical 2.0-liter turbodiesel quoted as "400 Nm at 2,000 rpm, 140 kW at 4,000 rpm". Feeding 400 Nm and 4,000 rpm into the formula returns 167.6 kW — a figure the engine never produces. The reason is that torque has already fallen away by the time the engine reaches its power peak; at 4,000 rpm it is making closer to 334 Nm, which is exactly the 140 kW on the brochure.
Going Backwards: kW to Nm
Rearranged, the same equation gives torque from power:
This direction is where the difference between an engine and an electric motor becomes obvious. Divide by a small rpm and the torque figure explodes — which is precisely why electric motors produce such large torque numbers at low speed, and why a gearbox multiplying torque at the wheels is doing the same arithmetic. The kW to Nm calculator handles that direction directly.
Why This Conversion Matters More for Electric Motors
Combustion engines are usually specified by their peak power, and the torque figure is supporting information. Electric motors are the other way round: they are characterised by a torque-and-speed envelope, because torque is what the magnetic field produces directly and power is the consequence.
- Below base speed an electric motor holds roughly constant torque, so power climbs almost linearly with rpm — double the speed, double the kilowatts.
- Above base speed the motor enters field weakening, torque tapers, and power flattens into a plateau.
- That plateau is the kW rating you see on the spec sheet, which is why an EV's peak power arrives across a band of speeds rather than at one point like an engine.
It is also why a motor rated "300 Nm, 150 kW" is not contradictory: 300 Nm is available from near zero rpm, but 150 kW only appears once the shaft passes roughly 4,775 rpm, where 300 × 4,775 ÷ 9,549 = 150.
Getting the Units Right First
The formula assumes newton-meters and revolutions per minute. Two conversions catch people out:
| If your figure is in | Do this first | Then |
|---|---|---|
| lb-ft | × 1.35582 to get Nm | Or use torque to HP directly |
| kgf·m | × 9.80665 to get Nm | Common on older Japanese spec sheets |
| rad/s | × 9.5493 to get rpm | Or use kW = Nm × rad/s ÷ 1,000 |
| Wheel torque | Divide by total gear ratio | Wheel torque is engine torque multiplied by gearing |
That last row is worth a moment. Wheel torque figures quoted for electric cars can run into thousands of newton-meters, but they are engine torque multiplied by the reduction gear. Putting wheel torque and engine rpm into the same formula produces a wildly overstated power figure.
If you need the answer in horsepower or PS rather than kilowatts, the Nm to HP calculator applies the equivalent constants.
Frequently Asked Questions
Use kW = (Torque in Nm × RPM) ÷ 9549. You need both the torque and the RPM at which it occurs.
It converts newton-meters and RPM into kilowatts, derived from 60,000 ÷ 2π. It's the metric equivalent of the 5252 constant used with pound-feet.
Convert to newton-meters first by multiplying by 1.3558, or use our torque to HP calculator which works in imperial units.
No. Power depends on how fast the torque is delivered, so RPM is required.
Multiply kilowatts by 1.341 to get mechanical horsepower.
It depends entirely on rpm. 300 Nm is 31.4 kW at 1,000 rpm, 94.2 kW at 3,000 rpm and 188.5 kW at 6,000 rpm. Torque alone cannot be converted to power.
No, and this is the most common mistake. Peak torque happens well below peak power, and by the redline torque has fallen substantially. Pairing them invents a figure the engine never makes.
Nm = (kW × 9,549) ÷ rpm. So 150 kW at 3,000 rpm is 477 Nm at that moment.
Because torque is available from near zero rpm, where the power figure is still small. Watch for wheel torque figures too — those are engine torque multiplied by the gear ratio, and must not be paired with engine rpm.