HP to PS Converter
Convert between imperial horsepower (HP/BHP) and metric horsepower (PS, pk, cv, ch, hk) — with kilowatts alongside.
European, Japanese and Korean car specs quote metric horsepower — written PS in Germany and Japan, pk in the Netherlands, ch/cv in France and Spain, hk in Scandinavia. Imperial (mechanical) horsepower is the US/UK unit. They differ by about 1.4%, enough to matter when comparing spec sheets.
HP to PS Formula
Why Two Horsepowers Exist
James Watt defined horsepower as 550 ft-lb/sec (745.7 W). When continental Europe metricated, engineers redefined it as the power to lift 75 kg one meter per second — 735.5 W — and called it Pferdestärke (PS, "horse strength"). Every country then translated the name: pk (paardenkracht), cv (cavallo vapore / caballo de vapor), ch (cheval-vapeur), hk (hästkraft). They are all the same 735.5 W metric unit — only the imperial HP differs.
Marketing exploits the gap: quoting PS makes the same engine sound ~1.4% stronger. EU type-approval documents use kW officially; see our HP to kW converter for that leg.
HP ↔ PS Conversion Table
| HP | PS | kW |
|---|---|---|
| 100 | 101.4 | 74.6 |
| 150 | 152.1 | 111.9 |
| 200 | 202.8 | 149.1 |
| 300 | 304.2 | 223.7 |
| 400 | 405.5 | 298.3 |
| 500 | 506.9 | 372.9 |
| 750 | 760.4 | 559.3 |
| 1000 | 1013.9 | 745.7 |
Worked Example
Where the 75-Kilogram Definition Came From
Watt's original horsepower was reverse-engineered from real horses turning a mill wheel: he settled on 33,000 foot-pounds per minute, a figure generous enough that no customer could accuse a steam engine of underperforming the animals it replaced.
When continental engineers metricated in the nineteenth century, they could not use feet or pounds, so they picked a round metric equivalent: the power to raise 75 kilograms one meter in one second. Multiply by standard gravity of 9.80665 m/s² and you get 735.49875 watts.
1 HP = 550 ft·lbf/s = 745.699872 W
The 75 kg figure was chosen because it produced a value close to Watt's horsepower without being absurdly precise. It landed 1.4% short, and that small gap has been quietly confusing car buyers ever since.
PS Is a Unit, Not a Rating Standard
A common misreading is that "PS" implies a particular test method. It does not — PS is only the unit. The standard governing how the engine was measured is separate, and matters more than the unit does.
| Standard | Reports in | Region & notes |
|---|---|---|
| DIN 70020 | PS | Historic German net standard. Still quoted for classic cars. |
| ECE R85 / EC 80/1269 | kW (often shown as PS too) | Current European type approval. Net, full production accessories. |
| JIS D1001 | PS | Japanese standard. Broadly comparable to DIN net. |
| SAE J1349 | hp | North American net certified. Corrected to 29.23 inHg dry, 77 °F. |
So a figure in PS could come from DIN, JIS or ECE, and a figure in hp could be SAE net or SAE gross. Converting the unit does not reconcile the standard — comparing a 1969 SAE gross number against a modern PS figure is meaningless no matter how carefully you multiply. See how horsepower is measured.
The 64 PS Kei Car Ceiling
Japan's kei jidōsha class carries tax and parking privileges in exchange for strict limits: 660 cc of displacement, capped dimensions, and — by voluntary manufacturer agreement — a maximum of 64 PS.
That is 63.1 imperial horsepower, or 47 kW. The number looks arbitrary in hp and perfectly round in kW, which tells you where it was actually set. As with Japan's old 280 PS ceiling for larger cars, it governed the advertised figure rather than what the engine necessarily produced, and turbocharged kei cars have long been suspected of quietly exceeding it.
It is worth knowing when importing: a kei car's spec sheet will read 64 PS regardless of how different two engines actually are.
When the 1.4% Actually Matters
The percentage never changes, but its practical significance does:
| Situation | Does it matter? | Why |
|---|---|---|
| Comparing two cars casually | No | 1.4% is inside the spread between two examples off the same production line. |
| Reading a magazine figure against a badge | Yes | Explains why a "200 PS" car is road-tested at 197 bhp — nothing is wrong. |
| Class or regulatory limits | Critically | A 64 PS or 35 kW cap has zero tolerance. Convert in the direction the rule is written. |
| Insurance and tax | Use kW instead | European systems work from the registration kW figure, not either horsepower label. |
| Quoting a dyno result | Overshadowed | Dyno-to-dyno variation is several percent — far larger than 1.4%. |
PS Outside the Car World
- Motorcycles. European and Japanese bikes are specified in PS or kW. License categories are written in kW, so convert before checking A1 or A2 eligibility — see motorcycle power-to-weight.
- Marine engines. Continental outboards and inboards often quote PS; US ratings are in hp at the propeller shaft.
- Industrial and agricultural machinery. European tractors are commonly badged in PS while the datasheet gives kW, and PTO power differs again from engine power.
- Historic aviation. German and Japanese wartime engine ratings are in PS, which is why figures quoted in English sources vary depending on whether the author converted.
Frequently Asked Questions
Almost — PS is about 1.4% smaller. 100 PS = 98.6 HP. For rough comparisons they're interchangeable; for exact figures, convert.
Yes. They're the Dutch, Italian/Spanish, French and Scandinavian names for the identical 735.5 W metric horsepower.
100 kW = 136.0 PS = 134.1 HP. Divide kilowatts by 0.7355 for PS, or by 0.7457 for imperial HP.
BHP (brake horsepower) is imperial HP measured at the crank — so BHP to PS uses the same ×1.0139 factor. See our brake horsepower page.
It was chosen as a round metric figure that landed close to Watt's original horsepower. Raising 75 kg one meter per second at standard gravity gives 735.49875 W — about 1.4% short of the imperial 745.7 W.
No. PS is only the unit — the test standard is separate. A PS figure could come from DIN 70020, JIS D1001 or ECE R85. Converting the unit does not reconcile different standards.
A voluntary manufacturer cap on the advertised figure for the kei class, alongside limits on displacement and dimensions. 64 PS is 63.1 hp or a round 47 kW — which tells you the limit was really set in kilowatts.
At regulatory limits, where there is zero tolerance — a 47 kW or 35 kW cap. For casual comparison it is inside normal production variation, and on a dyno result it is dwarfed by machine-to-machine spread.