Free engine power calculator · No sign-up · Runs entirely in your browser
Calculate engine power from torque and RPM in kilowatts, mechanical horsepower and metric horsepower (PS) — or estimate power from a 0–100 km/h time and kerb weight.
0–100 km/h → Estimated HP
| Unit | Value |
|---|
Use torque and RPM from the same point on the curve. Manufacturers quote peak torque at one engine speed and peak power at another. Entering peak torque alongside peak-power RPM produces a figure the engine never actually makes — often 20–30% too high.
Australian engines are rated in kilowatts at the flywheel, before drivetrain losses. Typical losses are around 10–15% for front-wheel drive, 15–18% for rear-wheel drive and 20–25% for all-wheel drive, so wheel power always reads below the manufacturer's figure. These are industry rules of thumb rather than measured constants.
Horsepower is a rate of doing work. James Watt coined it in the 1780s to sell steam engines to people who understood horses — he measured a dray horse turning a mill wheel and settled on 33,000 foot-pounds per minute as one horsepower. That figure was generous marketing rather than physics, but it stuck, and every horsepower number quoted since traces back to it.
Three variants are still in circulation, and they are not interchangeable:
| Unit | Equals | Used in |
|---|---|---|
| Mechanical horsepower (hp, bhp) | 745.7 W = 0.7457 kW | UK, USA |
| Metric horsepower (PS, ch, cv) | 735.5 W = 0.7355 kW | Europe, Japan |
| Kilowatt (kW) | 1,000 W | Australia, SI standard |
Almost every source gives you the formula and leaves the constant unexplained. It is not arbitrary — it falls straight out of Watt's definition.
The metric constant is the same derivation in SI units. Power in watts equals torque in newton-metres times angular velocity in radians per second, and RPM divided by 60 gives revolutions per second:
| Variable | Meaning | Typical range |
|---|---|---|
| Torque | Twisting force at the crankshaft | 150–600 Nm (cars), 1,500–3,000 Nm (trucks) |
| RPM | Crankshaft revolutions per minute | 1,200–2,200 (diesel), 4,000–8,000 (petrol) |
| 5,252 | 33,000 ÷ 2π | Fixed constant |
| 9,549 | 60,000 ÷ 2π | Fixed constant |
Australian specifications are in kilowatts; overseas reviews are usually in horsepower. The common figures:
| Kilowatts | Mechanical hp | Metric hp (PS) |
|---|---|---|
| 75 kW | 101 hp | 102 PS |
| 100 kW | 134 hp | 136 PS |
| 150 kW | 201 hp | 204 PS |
| 200 kW | 268 hp | 272 PS |
| 300 kW | 402 hp | 408 PS |
The shortcut worth memorising: kW × 1.34 gives horsepower, and horsepower ÷ 1.34 gives kilowatts. For any value not listed here, the horsepower converter handles all three units plus power-to-weight.
There are two independent tools on this page.
A 1.8-litre naturally aspirated engine produces 175 Nm at 4,000 rpm.
| Step | Calculation | Result |
|---|---|---|
| Power in kW | 175 × 4,000 ÷ 9,549 | 73.31 kW |
| Mechanical hp | 73.31 ÷ 0.7457 | 98.3 hp |
| Metric hp (PS) | 73.31 ÷ 0.7355 | 99.7 PS |
Typical of a small commuter car. Note how the PS figure reads 1.4 higher than hp for identical output — the same engine, two different horses.
A 2.0-litre bi-turbo diesel quotes 500 Nm at 2,000 rpm and 157 kW at 3,750 rpm. Running both points shows why one number never tells the whole story.
| Point on the curve | Calculation | Result |
|---|---|---|
| At peak torque (2,000 rpm) | 500 × 2,000 ÷ 9,549 | 104.7 kW (140.4 hp) |
| At peak power (3,750 rpm) | 157 × 9,549 ÷ 3,750 | Torque has fallen to 399.8 Nm |
A turbocharged petrol sports engine producing 400 Nm at 6,500 rpm.
| Step | Calculation | Result |
|---|---|---|
| Power in kW | 400 × 6,500 ÷ 9,549 | 272.3 kW |
| Mechanical hp | 272.3 ÷ 0.7457 | 365.1 hp |
Less torque than the diesel ute, nearly triple the power. Revs are doing the work: power is torque multiplied by engine speed, so spinning a smaller force much faster produces far more of it.
A 13-litre heavy-duty diesel producing 2,300 Nm at 1,200 rpm.
| Step | Calculation | Result |
|---|---|---|
| Power in kW | 2,300 × 1,200 ÷ 9,549 | 289.0 kW |
| Mechanical hp | 289.0 ÷ 0.7457 | 387.6 hp |
The truck makes more power than the sports car while turning at less than a fifth of the engine speed — because it produces nearly six times the torque. Which of the two accelerates harder is a different question entirely, and the next section answers it.
Horsepower on its own tells you very little about how a vehicle will feel. Power divided by mass tells you almost everything.
| Vehicle | Power | Kerb mass | kW per tonne |
|---|---|---|---|
| Small hatchback | 73.3 kW | 1,200 kg | 61 kW/t |
| Turbo diesel ute | 104.7 kW | 2,200 kg | 48 kW/t |
| Performance car | 272.3 kW | 1,500 kg | 182 kW/t |
| Heavy truck (B-double, laden) | 289.0 kW | 42,000 kg | 7 kW/t |
The truck has more power than the sports car and roughly one twenty-sixth of its power-to-weight ratio. That single ratio explains why a laden B-double takes minutes to reach highway speed while a sports car takes seconds — and why adding 200 kg of gear to a family car blunts it noticeably even though the engine is unchanged.
They measure different things, and the confusion between them drives most bad car-buying decisions.
| Torque | Power | |
|---|---|---|
| Measures | Twisting force | Rate of doing work |
| Units | Nm, lb-ft | kW, hp, PS |
| You feel it | Pulling away, climbing, towing | Top-end acceleration, high speed |
| Peaks at | Lower RPM | Higher RPM |
| Matters most for | Utes, trucks, towing, off-road | Overtaking, track work, high speed |
The honest summary: torque is what moves the load, power is what determines how quickly you can keep doing it. A tow vehicle wants torque low in the rev range. A car that overtakes confidently at 100 km/h wants power. Neither is universally better, and a vehicle chosen on the wrong one will disappoint in daily use.
Manufacturers quote power measured at the flywheel, on an engine dynamometer, with the gearbox and driveline removed. What reaches the road is less, because gears, differentials, driveshafts and tyres all absorb energy.
| Drivetrain | Typical loss | 200 kW at the flywheel becomes roughly |
|---|---|---|
| Front-wheel drive | 10–15% | 170–180 kW |
| Rear-wheel drive | 15–18% | 164–170 kW |
| All-wheel drive | 20–25% | 150–160 kW |
This is why a car advertised at 200 kW may read 165 kW on a chassis dyno. Nothing is wrong — the two numbers are measuring different places. Comparing a flywheel figure against a wheel figure is the single most common error in performance discussions.
| Vehicle type | Typical power | In horsepower |
|---|---|---|
| Small city car | 50–80 kW | 67–107 hp |
| Medium sedan or SUV | 110–150 kW | 148–201 hp |
| Dual-cab diesel ute | 110–190 kW | 148–255 hp |
| Large petrol SUV | 190–300 kW | 255–402 hp |
| Performance car | 250–450 kW | 335–603 hp |
| Motorcycle (road) | 25–150 kW | 34–201 hp |
| Heavy truck (prime mover) | 300–450 kW | 402–603 hp |
| Electric passenger car | 100–400 kW | 134–536 hp |
Power alone does not describe how an engine delivers it. For passenger vehicles, the drivetrain type matters as much as the number:
| Drivetrain | Typical power (passenger) | Peak power arrives | Character |
|---|---|---|---|
| Petrol | 70–250 kW | 5,000–7,000 rpm | Needs revs; rewards a downshift |
| Turbo diesel | 100–190 kW | 3,000–4,000 rpm | Strong low-end torque, narrow band |
| Hybrid | 80–220 kW | Combined engine + motor | Electric fills the gap before the engine wakes up |
| Electric | 100–400+ kW | From standstill | Full torque immediately, usually no gears |
Every quoted figure comes from a dynamometer, and the standard used matters:
Test standards differ too. SAE J1349 (North America), DIN 70020 and ISO 1585 (Europe) each specify their own ambient temperature, pressure and accessory-load corrections. The same engine tested to different standards can post noticeably different numbers without a single component changing — another reason to check which standard a figure comes from before comparing two vehicles.
Power is almost never what stops you towing. Three ratings on the compliance plate do, and one of them catches people out constantly:
| Rating | What it limits |
|---|---|
| Maximum braked towing capacity | The heaviest trailer the vehicle may tow, with trailer brakes fitted |
| GVM — Gross Vehicle Mass | The vehicle itself, fully loaded, including passengers, fuel, accessories and towball download |
| GCM — Gross Combination Mass | Vehicle and trailer together, fully loaded |
Once you are within those limits, power and torque decide how the job feels — whether the vehicle holds 100 km/h up a long grade without hunting through gears, and how hot the transmission runs. That is a comfort and longevity question, not a legal one.
How do you calculate engine horsepower?
Multiply torque by engine speed and divide by a constant. In imperial units: hp = torque (lb-ft) × RPM ÷ 5,252. In metric: kW = torque (Nm) × RPM ÷ 9,549, then divide kW by 0.7457 for mechanical horsepower. An engine making 400 Nm at 5,000 rpm produces 400 × 5,000 ÷ 9,549 = 209.4 kW, or about 281 hp.
What is the formula for horsepower?
hp = torque × RPM ÷ 5,252, where torque is in pound-feet. The 5,252 comes from Watt's definition of one horsepower as 33,000 foot-pounds per minute, divided by 2π to convert revolutions into radians. The metric equivalent divides by 9,549, which is 60,000 ÷ 2π.
Why do horsepower and torque curves always cross at 5,252 RPM?
Because horsepower is defined as torque × RPM ÷ 5,252. When RPM equals 5,252, the multiplication and division cancel out and the two values are numerically identical. On any dyno chart plotting horsepower and pound-feet on the same scale, the curves intersect there — on every engine ever built.
What is the difference between HP and kW?
They measure the same thing in different units. One mechanical horsepower equals 0.7457 kW, so kW × 1.341 gives horsepower. Australia rates engines in kilowatts under its design rules, while the UK and USA use horsepower. Metric horsepower (PS) is a third unit again, equal to 0.7355 kW.
What is brake horsepower?
Brake horsepower (bhp) is power measured at the flywheel using a brake-type dynamometer, before any drivetrain losses. The name comes from the braking device used to load the engine during testing. In practice bhp and flywheel horsepower mean the same thing.
What is wheel horsepower?
Wheel horsepower is measured at the driven wheels on a chassis dynamometer, so it is what actually reaches the road. It runs roughly 10–15% below flywheel figures on front-wheel drive, 15–18% on rear-wheel drive and 20–25% on all-wheel drive, depending on transmission and conditions.
Does torque affect horsepower?
Directly — horsepower is calculated from torque and engine speed, so you cannot change one without affecting the other. Raising torque at a given RPM raises power proportionally. Two engines can reach the same peak power very differently: high torque at low revs, or moderate torque spun much faster.
How much horsepower does my car have?
Check the compliance plate, owner's manual or the manufacturer's specification — Australian vehicles are rated in kilowatts. If you know peak torque and the RPM it occurs at, this calculator will give you the power at that point. For a measured figure rather than a quoted one, a chassis dyno run is the only reliable answer.
Is more horsepower always better?
No. Higher power generally means a larger, thirstier engine, higher purchase price and higher insurance. For towing, low-rpm torque matters far more than peak power. For daily commuting, a modest engine in a light car often feels quicker in traffic than a powerful one in a heavy vehicle, because power-to-weight is what you actually experience.
What is a good horsepower for daily driving?
For most Australian driving, 90–120 kW (120–160 hp) in a car under 1,600 kg is comfortable — enough to merge and overtake without strain. Around 55–70 kW per tonne is a useful benchmark. Regular towing or frequent highway overtaking with a full load justifies more; suburban commuting rarely does.
Does horsepower affect fuel economy?
Indirectly. Power itself does not burn fuel — using it does. A larger engine typically carries more internal friction and mass, so it consumes more even at light load. But a small engine worked hard can use more than a larger one loafing. What you spend depends far more on how you drive than on the number in the brochure; work out your own figure with the gas mileage calculator.
How does horsepower affect towing?
Towing capacity is set by the manufacturer based on chassis, braking and cooling — not by power. What power and torque determine is how comfortably the vehicle handles the load: whether it holds highway speed up a long grade, and how hard the transmission works. Low-rpm torque is the more useful quality, which is why diesel utes dominate towing in Australia despite modest peak power. When comparing tow vehicles, check the maximum braked towing capacity and the Gross Combination Mass on the compliance plate, not the power figure.
Power is one number in a much larger picture. An engine that looks strong on paper may be expensive to run, and a modest one in a light car may be more satisfying day to day than the specification suggests. Before buying or modifying, weigh the power figure against consumption and running costs — check efficiency with the gas mileage calculator, price the fuel with the fuel cost calculator, and convert between power units with the horsepower converter.