Horsepower to Metric Horsepower: hp and PS Side by Side

Reconciling a US Horsepower Figure with a German PS Claim

Open an American road test and a German press release for the same car and the engine appears to have two different outputs. The US page says 503 hp; the Stuttgart page says 510 PS. Nothing was changed between the two markets — the two press offices are describing identical watts against two different definitions of one horse.

Conversion factor: 1 hp = 1.013869665 PS, so multiply the horsepower figure by roughly 1.0139. A 503 hp BMW M3 Competition works out at 509.98 PS — which is exactly why the German brochure prints 510 PS.

Two Horses, Two Yardsticks

The 550 ft·lb/s horse

Mechanical horsepower comes from James Watt's estimate of a pit pony's work rate: 550 foot-pounds every second, which lands on 745.69987 W. This is the horse behind every American and British engine figure.

The 75 kgf·m/s horse

Continental Europe rebuilt the same idea in metric units — lifting 75 kg one metre in one second — which gives 735.49875 W. A smaller horse, so it takes more of them to describe the same engine.

A gap of about 1.4 per cent

The two definitions differ by 10.2 W, so the PS number always runs about 1.4 % above the hp number. On a 200 hp hatchback that is three units; on a 700 hp supercar it is nearly ten.

Model names built on the bigger number

European names that carry an output — Trophy 300, A110 S 300 — are counting metric horses. The identical car reaches an American price list at 296 hp, and the badge suddenly looks wrong by four units.

Putting Two Road Tests in One Column

Whether you are building a comparison table, settling a forum argument or checking whether a rival really is more powerful, the routine is the same: normalise both cars to one unit before you compare anything else.

Enter the horsepower the road test printed

Type the figure into the left field — 380, 503, 717 — and the metric equivalent appears as you type. A comma works as a decimal point, so 503,5 reads the same as 503.5, and stray spaces are ignored.

Hold the result against the maker's own PS claim

If the converted value lands within a unit of the European figure, both offices are quoting one engine. A gap of five or more usually means a different state of tune, a different fuel grade or a market-specific exhaust.

Turn it around when the source is European

Press the swap button (↔) to run PS → hp and drop a Munich or Maranello figure into an American comparison. By hand, multiply the metric figure by 0.98632: 630 PS becomes 621.4 hp.

Lift the plain number into your table

The copy button places the bare figure on the clipboard with no unit attached, which is what a spreadsheet cell or a forum table wants. Ctrl + C inside a field does the same.

Marketing rounds, the arithmetic does not: the 992-generation 911 Turbo S is sold as 650 PS, yet its 640 hp figure converts to 648.9. Brochures round up to the nearest tidy ten, so a converted value sometimes sits a point or two below the badge.

Performance Cars as Quoted on Both Sides of the Atlantic

Eight engines that appear in the enthusiast press in both currencies. The middle columns hold the same output written twice; the last shows how far apart the two headlines look.

Model	Quoted in hp	Same output in PS	Gap
Volkswagen Golf GTI (Mk8)	241 hp	244.3 PS	+3.3
Porsche 911 Carrera (992)	380 hp	385.3 PS	+5.3
BMW M3 Competition (G80)	503 hp	510.0 PS	+7.0
Audi RS 6 Avant (C8)	591 hp	599.2 PS	+8.2
Mercedes-AMG GT 63 S	621 hp	629.6 PS	+8.6
Lamborghini Huracán EVO	631 hp	639.8 PS	+8.8
Porsche 911 Turbo S (992)	640 hp	648.9 PS	+8.9
Dodge Challenger SRT Hellcat	717 hp	726.9 PS	+9.9

Read down the last column and the pattern is plain: the gap is a fixed percentage, not a fixed number, so it barely registers on a warm hatchback and becomes a headline of its own on a supercar. It also explains why so many European figures land on round hundreds — 385, 510, 600, 630, 650 — while their American twins sit on awkward values such as 380, 503, 591 and 631.

What Helps When You Are Cross-Checking Spec Sheets

Both columns of the comparison move together

Each field is editable and the other tracks it instantly, so you can run through a whole model range — base, S, Competition — without clearing anything between cars.

Flip when the press release is German

One press of the swap arrows turns the page into a PS → hp tool, the direction you want when the source material came out of a European launch event.

Every unit a road test might quote

Searchable dropdowns on both sides carry kW as well, so an output written for a European technical table drops straight into the same comparison.

Decimals for the borderline badges

Results carry up to eight decimal places, which is what settles an argument over whether a maker rounded up or genuinely found a couple of extra units.

Questions Enthusiasts Ask About hp and PS

Why does the same engine make more PS than hp?

Because a metric horse is the weaker animal. One PS is 735.49875 W against 745.69987 W for one mechanical horsepower, so it takes about 1.4 % more of them to describe the same engine. The car gained nothing crossing the border; the ruler shrank.

Are CV, ch, pk and cv the same thing as PS?

Yes — one 735.49875 W unit under local names. PS is Pferdestärke in German, ch is cheval-vapeur in French, CV is cavallo vapore in Italian and caballo de vapor in Spanish, pk is paardenkracht in Dutch, and Japanese catalogues write PS in Latin letters. One trap: French CV fiscaux is a tax class and not this unit at all.

A British magazine quotes bhp — is that a third figure?

No. In a car context bhp means brake horsepower — output read at the flywheel on a brake dynamometer — and it uses the same 745.7 W mechanical horse, so treat a bhp road-test figure as hp when you convert it. Watch the abbreviation elsewhere though: in this converter's unit list bhp is boiler horsepower, a separate 9 809.5 W steam-raising unit with no connection to engines.

Why do European model names carry the PS number rather than hp?

Because the name is written for the home market, where PS is the familiar unit — and it happens to be the larger of the two. A Renault Mégane R.S. Trophy 300 or an Alpine A110 S 300 carries 300 PS, which converts to 295.9 hp. American listings print 296, so the name and the specification appear to disagree while describing one engine.

Which unit will a manufacturer publish in which market?

As a rule: hp in the United States, bhp in the British motoring press, PS across Germany, Austria and Switzerland, ch in France, CV in Italy and Spain, pk in the Netherlands, and PS again in Japan and Korea. Many European makers now print PS and kW side by side, so one engine can carry two numbers on its home spec sheet and a third once an American edition converts it.

Horsepower to Metric Horsepower