kW vs Nm: What the Two Numbers Actually Mean

Q: What is the difference between kW and Nm?

Newton metres measure torque, the rotational force an engine produces. Kilowatts measure power, the rate at which it does work. Torque exists even when nothing is moving, while power only exists when something is rotating.

Q: How do you convert kW to Nm?

Multiply kilowatts by 9549 and divide by RPM. The conversion is impossible without knowing engine speed, because the same power gives high torque at low RPM and low torque at high RPM.

Q: Is more Nm or more kW better?

They serve different purposes. Torque determines how effortlessly a car pulls at low revs, which matters for towing and relaxed driving. Power determines top speed and hard acceleration. Most drivers notice torque more in everyday use.

Q: Why do diesels have high Nm but low kW?

Because diesels are limited by their rev ceiling. Power depends on both torque and RPM, so an engine producing large torque at only 2,000 RPM cannot generate a high power figure no matter how strong it is.

Q: Do kW and Nm curves cross like HP and torque do?

In theory at 9,549 RPM, but that is above the rev limit of nearly every road engine, so on a metric dyno plot the curves usually never cross. The imperial crossover at 5,252 RPM is visible because it falls within the normal rev range.

Q: Why do electric cars feel quick with ordinary power figures?

Because electric motors deliver near-peak torque from zero RPM without waiting for revs to build or gears to change. The torque curve is close to flat rather than a hump, so the response is immediate.

Every European spec sheet lists both. They are not two ways of saying the same thing — and the link between them is engine speed.

Last updated 1 August 2026 · 6 min read

↓ The difference ↓ How RPM links them ↓ Which matters ↓ FAQ

A European brochure will tell you a car makes 150 kW and 320 Nm. Those are not alternative descriptions of the same thing — they answer different questions, and a car can be strong on one and unremarkable on the other.

In one line: Nm is how hard the engine twists. kW is how quickly it can do that twisting, over and over.

What Each One Measures

Newton metres measure torque — rotational force. One newton metre is one newton of force applied at one metre from the centre of rotation. It is a static quantity: a spanner on a bolt applies torque even when nothing moves.

Kilowatts measure power — the rate of doing work. Power only exists when something is actually moving. An engine producing enormous torque at zero RPM produces zero power.

The everyday analogy that holds up: torque is how heavy a load you can lift; power is how many you can lift per minute. A strong person who works slowly and a lighter person who works quickly can shift the same tonnage in an hour.

How RPM Links the Two

The relationship is fixed and simple:

Formula

kW = Nm × RPM ÷ 9549

Rearranged: Nm = kW × 9549 ÷ RPM. The constant 9549 is 60 × 1000 ÷ 2π, converting RPM to radians per second and watts to kilowatts.

This is why the same torque produces wildly different power depending on where in the rev range it appears:

Torque	At 1,500 RPM	At 3,000 RPM	At 6,000 RPM
200 Nm	31.4 kW	62.8 kW	125.7 kW
320 Nm	50.3 kW	100.5 kW	201.1 kW
500 Nm	78.5 kW	157.1 kW	314.2 kW

A diesel making 500 Nm at 2,000 RPM produces about 105 kW. A racing engine making a modest 200 Nm at 9,000 RPM produces 188 kW — nearly twice the power from under half the torque, purely because it spins faster.

Which Number Should You Care About?

Both, for different parts of driving.

Torque decides how the car feels. Strong low-RPM torque means the car pulls without downshifting — relaxed overtaking, easy towing, no need to rev.
Power decides ultimate performance. Top speed and hard acceleration through the gears depend on power, because that is what determines how fast work gets done.
Peak figures happen at different speeds. A turbo engine might make maximum torque from 1,800 RPM but peak power near 5,500. Feeding both headline numbers into the formula together will not reproduce either.

Gearing complicates the picture usefully. A gearbox multiplies torque, so a low-torque high-revving engine with short gears can out-accelerate a high-torque engine with tall ones. This is why quoted engine torque tells you less about acceleration than people assume — what reaches the wheels has been through a gear ratio first.

The Metric Version of the 5252 Rule

In imperial units, horsepower and torque curves always cross at 5,252 RPM. The metric equivalent is less tidy: kW and Nm curves cross wherever kW = Nm, which from the formula happens at 9,549 RPM — above the rev ceiling of nearly every road engine.

So on a metric dyno plot the two curves usually never cross at all, with torque sitting numerically above power across the whole range. That is a quirk of the units, not a difference in physics. Our guide to the 5252 rule explains the imperial version in full.

Electric Motors Change the Shape

Electric motors produce near-maximum torque from zero RPM, which is why an ordinary electric car feels so brisk away from a standstill. Power still builds with speed, so the peak kW figure arrives higher up — but the torque curve is close to flat rather than a hump.

This is also why comparing an EV's torque figure directly against a petrol car's is misleading. The EV delivers its torque instantly and without gear changes, so the same number produces a very different experience.

Converting Between Them

You cannot convert kW to Nm or back without RPM — the formula requires it, and any tool that returns an answer without asking for engine speed is assuming a value silently. Use our kW to Nm calculator or Nm to kW, both of which ask for the speed the figure applies to.

For imperial equivalents see HP to torque and Nm to lb-ft, and for the broader relationship horsepower vs torque.

How this guide is sourced

Uses the exact relationship P = T x omega, with the constant 9549.30 derived from 60 x 1000 divided by 2 pi. Table values are computed at full precision and rounded for display. Statements about engine behaviour describe general characteristics of naturally aspirated, turbocharged and electric powertrains rather than any specific model.

Frequently Asked Questions

What is the difference between kW and Nm?

Nm measures torque — rotational force. kW measures power — the rate of doing work. Torque exists even at a standstill; power only exists when something rotates.

How do you convert kW to Nm?

Multiply kW by 9549 and divide by RPM. It is impossible without engine speed — the same power gives high torque at low RPM and low torque at high RPM.

Is more Nm or more kW better?

Different purposes. Torque determines low-rev pull — towing and relaxed driving. Power determines top speed and hard acceleration. Most drivers notice torque more day to day.

Why do diesels have high Nm but low kW?

Diesels are limited by rev ceiling. Power depends on torque and RPM, so large torque at only 2,000 RPM cannot produce a high power figure.

Do kW and Nm curves cross like HP and torque do?

In theory at 9,549 RPM — above nearly every road engine rev limit, so metric plots usually never cross. The imperial 5,252 RPM crossover falls within the normal range.

Why does my car feel fast despite low kW?

Usually gearing and torque delivery. A gearbox multiplies torque, so short gears make a modest engine feel urgent — and low weight matters more than either figure.

Why do electric cars feel quick with ordinary power figures?

Electric motors deliver near-peak torque from zero RPM, with no revs to build or gears to change. The torque curve is close to flat rather than a hump.