Convert horsepower to kilowatts, calculate horsepower from torque and RPM, or work out power from force and velocity. All three modes in one tool, using exact SAE and SI conversion factors — not the rounded textbook approximations.
Horsepower is a unit of power — the rate at which work is done or energy is transferred. It was coined by James Watt in 1782 as a marketing tool: he needed a way to tell customers how many draft horses his steam engines would replace. Watt settled on 33,000 foot-pounds of work per minute as one 'horsepower,' which corresponds to 745.7 watts in modern SI units. Today, horsepower remains the dominant power unit for automobiles in the US, alongside kilowatts (SI standard) and metric horsepower (PS) used in continental Europe. The three are close cousins — 1 HP = 0.7457 kW = 1.014 PS — but the small differences matter when comparing spec sheets across manufacturers and markets.
Power can be calculated from many starting points. This calculator handles the three most common in everyday and automotive use:
You already know power in some unit — HP, kW, PS, watts — and you want it expressed in another. Type a value in any field and all others update instantly. Most common: converting between US spec sheets (HP) and European spec sheets (kW or PS).
The engineering formula. You know an engine's torque output (typically in N·m or ft·lb) and the RPM at which it makes that torque. Power = Torque × angular velocity, which is where the famous '/5252' constant comes from. This is the formula manufacturers use to publish peak HP numbers.
The mechanical-power formula. Power = Force × Velocity. Useful for problems like: how much HP does a cyclist need to overcome drag at 40 km/h? Or: how much HP does a pump need to lift water at a given flow rate? Or: how much HP to drag a sled at a constant speed?
Each calculation mode uses a different equation. Here's what each one means and where the constants come from.
Torque in ft·lb, RPM in revolutions per minute. The 5252 isn't arbitrary — it's 33,000 ÷ 2π. Watt defined 1 HP = 33,000 ft·lbf per minute, and one revolution covers 2π radians, so the constant works out to 5252.113. As a side effect, every engine's torque curve and HP curve cross at exactly 5252 RPM.
Torque in N·m, RPM converted to angular velocity in rad/s. The pure SI form. RPM × 2π converts revolutions to radians; the / 60 converts per-minute to per-second. The result is in watts, which you can convert to HP (÷745.7) or kW (÷1000).
Force in newtons, velocity in m/s — gives power in watts. The most fundamental power equation. Imperial form: HP = (F[lbf] × v[ft/s]) / 550, where 550 is the original Watt definition. Useful for cycling power, drag-racing analysis, or any constant-velocity problem where you know the resistance force.
Common conversions you can do mentally or verify against this table. The calculator uses exact values; these are rounded to 4 significant figures.
| Value | kW | PS | Watts | ft·lbf/s |
|---|---|---|---|---|
| 1 HP (mechanical) | 0.7457 kW | 1.014 PS | 745.7 W | 550 ft·lbf/s |
| 1 kW | 1.341 HP | 1.360 PS | 1000 W | 737.6 ft·lbf/s |
| 1 PS (metric HP) | 0.9863 HP | 0.7355 kW | 735.5 W | 542.5 ft·lbf/s |
| 100 HP | 74.57 kW | 101.4 PS | 74 570 W | 55 000 ft·lbf/s |
| 100 kW | 134.1 HP | 136.0 PS | 100 000 W | 73 760 ft·lbf/s |
| 500 HP (sports car) | 372.8 kW | 507.0 PS | 372 850 W | 275 000 ft·lbf/s |
| 1 HP (electrical) | 0.746 kW | 1.014 PS | 746 W | 550.2 ft·lbf/s |
What 'normal' looks like, from compact cars to supercars. All numbers are manufacturer-rated peak HP at standard conditions.
| Vehicle | HP (mech.) | kW | PS |
|---|---|---|---|
| Honda Civic LX (1.5L turbo, 2024) | 158 HP | 118 kW | 160 PS |
| Toyota Camry LE (2.5L, 2024) | 203 HP | 151 kW | 206 PS |
| Toyota RAV4 (2.5L, 2024) | 203 HP | 151 kW | 206 PS |
| Ford F-150 EcoBoost 2.7L (2024) | 325 HP | 242 kW | 330 PS |
| BMW M3 Competition (S58, 2024) | 503 HP | 375 kW | 510 PS |
| Tesla Model 3 Performance (2024) | 510 HP | 380 kW | 517 PS |
| Porsche 911 Turbo S (2024) | 640 HP | 478 kW | 650 PS |
| Bugatti Chiron Super Sport | 1577 HP | 1176 kW | 1600 PS |
Both measure the same thing — power. Different parts of the world just default to different units. Here's the practical comparison.
The traditional automotive power unit, defined by James Watt in 1782 and still standard in US car specs. 1 HP = 745.7 W exactly.
The SI unit for power. Used in European and Asian car specs, all electric-motor ratings, and any engineering work. 1 kW = 1000 W = 1.341 HP.
| Property | Horsepower | Kilowatts |
|---|---|---|
| 1 unit equals | 745.7 W | 1000 W |
| Mental conversion | ÷ 1.341 → kW | × 1.341 → HP |
| Where used | US automotive | EU automotive + EVs |
| Defined by | James Watt (1782) | SI system (1960) |
| Subtypes | Mechanical, electrical, metric (PS) | None — just one definition |
| Used in EV specs | Mostly for US marketing | Always — internal standard |
Confusingly, 'horsepower' means slightly different things in the US versus continental Europe. Cars sold globally often have both numbers on the spec sheet.
The Watt-era definition: 1 HP = 550 ft·lbf/s = 745.6999 W. Used in US/UK/Canada/Australia, and in most English-language automotive press worldwide.
The continental European definition: 1 PS = 75 kgf·m/s = 735.49875 W. About 1.4% smaller than mechanical HP. Called PS in German, CV in French/Spanish, cv in Italian/Portuguese.
| Property | Mechanical HP | Metric HP (PS) |
|---|---|---|
| Defined as | 550 ft·lbf/s | 75 kgf·m/s |
| In watts (exact) | 745.6999 W | 735.49875 W |
| Ratio to kW | 1 kW = 1.341 HP | 1 kW = 1.360 PS |
| 1 HP in PS | — | 1 HP = 1.014 PS |
| Where used | US, UK, AUS | EU continent, BR |
| Difference | Baseline | 1.4% smaller |
These two get mixed up constantly in car discussions. They're related but they measure different things — and they peak at different RPMs.
The twisting force the engine produces. Measured in N·m or ft·lb. Determines how hard the car can push from a standstill — towing capacity, acceleration off the line, climbing steep grades.
The rate at which torque is delivered — torque times RPM, divided by 5252. Determines how fast the car can go (top speed) and how quickly it can accelerate at higher speeds.
| Property | Torque | Horsepower |
|---|---|---|
| What it measures | Twisting force | Rate of work |
| Direct unit | N·m or ft·lb | kW or HP |
| What you feel | Pulling from stop | High-speed push |
| Best engine type | Diesel, turbo gas | Naturally aspirated, high-revving |
| Peak RPM | Lower (2000–4000) | Higher (5000–8000) |
| At 5252 RPM | Numerically equals HP | Numerically equals torque |
A Honda Civic 1.5L turbo produces 138 lb·ft of torque at 5000 RPM. Plugging that into HP = (138 × 5000) / 5252 gives 131.4 HP at that specific RPM. Honda's published peak of 158 HP comes at 6000 RPM, because peak HP usually occurs at a higher RPM than peak torque.
An elite cyclist holding 40 km/h (11.1 m/s) against 50 N of aerodynamic drag is outputting Power = 50 × 11.1 = 556 W, which works out to 0.75 HP. That matches well with the real-world observation that elite cyclists sustain around 400 W for a one-hour effort and burst to 1000+ W for short sprints.
A heavy-duty diesel making 1000 N·m of torque at 1800 RPM produces Power = 1000 × 1800 × (2π / 60) ≈ 188,500 W. That converts to about 252 HP or 188 kW — squarely in the range of a Cummins ISL midrange truck engine.
If your engine spec is in lb·ft (US), use the lb·ft option. If in N·m (most of the rest of the world), use N·m. Don't manually convert — let the calculator do it.
'Peak HP' in spec sheets is at the engine's peak-HP RPM, not at any RPM. If you calculate using torque at a different RPM, you'll get a different (and usually lower) HP number.
Brake horsepower (BHP) is measured at the crankshaft, before transmission/differential losses. Wheel horsepower (WHP) is what reaches the wheels — typically 10–20% lower for cars with automatic transmissions.
Manufacturer HP figures for EVs are usually derived from peak kW × 1.341. The HP value is essentially marketing translation — kW is the real spec.
Naturally-aspirated engines lose roughly 3% of HP per 1000 ft of elevation. Turbocharged engines are mostly altitude-compensating up to their boost limit. Manufacturer specs assume sea level + standard conditions.
If you compare '200 PS' from a German brochure with '200 HP' from a US brochure, you're comparing slightly different units. 200 PS is really about 197 mechanical HP.
An engine can have lots of torque at low RPM but little HP, or vice versa. Without RPM, 'how much HP?' is unanswerable.
The formula gives HP at the specific RPM you input. Peak HP is the maximum across all RPMs — usually at much higher RPM than peak torque.
Using ft·lb torque with the metric formula (or N·m with the /5252 formula) will give you nonsense. Always normalize first, or use a calculator that does it for you.
A car advertised at 300 BHP typically puts ~250 HP to the wheels (about 15% drivetrain loss for an automatic). Dyno measurements at wheels will always be lower than advertised specs.
Because horsepower was defined before the watt was an internationally-standardized unit. James Watt picked 33,000 ft·lbf per minute based on his observations of mill horses — a unit that happens to convert to 745.6999 watts. The metric system arrived later and standardized power around the watt, but the older HP unit stuck around in automotive use. There's no deeper reason it isn't a round number.
Briefly, yes. An average healthy adult can produce about 1 HP (745 W) for 6–10 seconds during peak effort — a hard sprint or a heavy lift. For sustained work over an hour, a fit person produces around 100–200 W (0.13–0.27 HP). Elite cyclists can sustain ~400 W for an hour. Over a full work day, sustainable human output is closer to 75 W.
As of 2026, the highest-HP production cars are mostly limited-edition hypercars: the Koenigsegg Jesko Absolut and the Lotus Evija both claim around 2000 HP. The Bugatti Chiron Super Sport sits at 1577 HP, the Rimac Nevera at 1914 HP. EV powertrains have made these numbers much easier to reach — electric motors don't have the same RPM and breathing limits that constrain combustion engines.
Combustion engines need oxygen, and high-altitude air has less of it per cubic meter. Denver (~5000 ft) has about 85% the oxygen density of sea level, so a naturally-aspirated engine there makes roughly 85% of its sea-level power. Turbocharged engines compensate by compressing intake air, so they lose much less — a turbo engine might keep 95% of its sea-level HP at Denver. Above the turbo's pressure limit, even forced-induction engines lose power.
You can't directly — they measure different things. Watts (the connection) = Volts × Amps. So if you know voltage: Amps = (HP × 745.7) / Volts. A 1 HP electric motor on a 120 V circuit pulls about 6.2 amps, ignoring inefficiency. Real motors are 80–95% efficient, so add 5–25% to that estimate. The horsepower of an electric motor is its mechanical output; the wattage you see on the spec sheet is its electrical input.
Horsepower is a unit of power — the rate of doing work. 1 mechanical horsepower equals 550 foot-pounds of work per second, or 745.7 watts. It was introduced by James Watt in the late 1700s to help his customers compare his steam engines to the draft horses they replaced. Today it's still the standard automotive power unit in the US, alongside kilowatts (SI) and PS (metric horsepower) used elsewhere.
Use HP = (Torque × RPM) / 5252, where torque is in foot-pounds and RPM is engine speed. The 5252 comes from 33,000 ft·lbf per minute (the original Watt definition) divided by 2π. So a 300 ft·lb engine at 5000 RPM produces (300 × 5000) / 5252 ≈ 286 HP. In metric: Power [W] = Torque [N·m] × RPM × (2π / 60), which our calculator handles automatically.
Both measure power; they're just different units. 1 mechanical HP = 0.7457 kW exactly, so 1 kW ≈ 1.341 HP. US car specs traditionally use HP; European specs use kW (or PS, which is slightly different again). A 200 kW car is about 268 HP — a fair amount more than the common rounding 'kW × 1.34' suggests when you do it imprecisely.
Mechanical HP (used in the US, sometimes called 'imperial HP' or 'brake HP/BHP') is defined as 550 ft·lbf/s = 745.6999 W. Metric HP (called PS in Germany, CV in France) is defined as 75 kgf·m/s = 735.49875 W. The difference is about 1.4%, so a car listed as '200 PS' is really about 197 HP. Most modern manufacturers also publish kW alongside to avoid the confusion.
It comes from the original definition. James Watt set 1 HP = 33,000 ft·lbf per minute. Since RPM measures revolutions per minute and one revolution covers 2π radians, the formula HP = (Torque × RPM) / 5252 falls out: 33000 / (2π) = 5252.113. As a side effect, every engine's torque and HP curves intersect at exactly 5252 RPM — at that speed, the two numbers are mathematically identical.
In modern usage, yes — BHP and mechanical HP refer to the same unit (745.7 W). The 'brake' originally meant the engine power measured at the output shaft using a mechanical brake-style dynamometer, before drivetrain losses. Today 'BHP' and 'HP' are used interchangeably in automotive specs. Wheel horsepower (WHP), measured at the wheels after drivetrain losses, is typically 10–20% lower than BHP.
Modern compact cars typically have 150–200 HP (e.g., Honda Civic ~158 HP). Mid-size sedans run 200–300 HP (Toyota Camry V6 ~301 HP). Sports cars start around 300 HP and go up. Pickup trucks like the Ford F-150 EcoBoost range from 325–450 HP. Electric vehicles often have higher HP than equivalent gas cars because electric motors deliver peak torque from 0 RPM. The Tesla Model 3 Performance is ~510 HP.
Surprisingly, only about 1 HP at sustained output — and James Watt deliberately defined it that way. A horse pulling a load can output 10–15 HP in short bursts (a few seconds), but for sustained work over an hour or more, 1 HP is roughly accurate. So Watt's marketing claim that 'this engine equals 10 horses' was technically generous to the horses if measured by peak output.
Conversion factors are exact per the cited standards. Vehicle HP figures are from manufacturer spec sheets at time of publication.