Convert metric horsepower (PS) to mechanical horsepower. One PS is 0.9863 hp — why the same engine has two power figures.

The formula

hp = PS × 0.98632007

A metric horsepower is 75 kilogram-force metres per second — exactly 735.49875 W. Mechanical horsepower is 550 foot-pounds-force per second — 745.6998716 W. The ratio is the number above.

A PS is 1.4% smaller than an hp.

Why the same engine has two power figures

This is the whole reason the page exists. A manufacturer quotes whichever unit its market expects, and the two are close enough that the difference reads as a specification change rather than a unit change:

PS	hp	kW
90 PS	88.8 hp	66.2 kW
100 PS	98.6 hp	73.5 kW
130 PS	128.2 hp	95.6 kW
150 PS	147.9 hp	110.3 kW
200 PS	197.3 hp	147.1 kW
250 PS	246.6 hp	183.9 kW
300 PS	295.9 hp	220.6 kW
400 PS	394.5 hp	294.2 kW
500 PS	493.2 hp	367.7 kW

A car reviewed as “197 hp” in Britain and “200 PS” in Germany is one car. The round number is always in the unit the figure was originally quoted in — 200 PS is the manufacturer’s number and 197.3 hp is the conversion, not the other way round.

The same unit under many names

Written	Language	Value
PS (Pferdestärke)	German	735.49875 W
cv (cavallo vapore, cheval vapeur)	Italian, French	735.49875 W
pk (paardenkracht)	Dutch	735.49875 W
hk (hästkraft)	Swedish	735.49875 W
CV	Spanish, Portuguese	735.49875 W
馬力 / 匹	Chinese, Japanese	735.49875 W

All identical. The Chinese 馬力 and Japanese 馬力 are metric horsepower, so a Japanese or Taiwanese spec sheet quoting 馬力 is quoting PS, not hp.

French fiscal horsepower (chevaux fiscaux, CV) is not this unit at all. It is a tax band computed from engine capacity and emissions, and has no fixed relationship to power.

Quick reference

PS	hp
1 PS	0.986 hp
1.014 PS	1 hp
10 PS	9.86 hp
100 PS	98.63 hp
500 PS	493.16 hp
1000 PS	986.32 hp

When the difference matters

At 100 PS the gap is 1.4 hp — inside the tolerance of any dynamometer, and not worth arguing about. At 700 PS it is nearly 10 hp, which is enough to matter in a comparison between two cars quoted in different units.

Where it always matters is in not converting twice. A figure already converted from PS to hp and then read as PS again drifts by 2.8%.

Estimating in your head

Take off 1.4%, which for most purposes means the numbers are the same. 200 PS is “about 197 hp”; anything more precise wants the multiplier.

Metric horsepower (PS) to horsepower