Horsepower Converter
Convert between mechanical horsepower (hp), metric horsepower (PS / ch / CV), electrical hp, boiler hp, watts, kilowatts, BTU per hour and foot-pounds per second.
200 Mechanical horsepower (hp, imperial) =
149.14
Converted via 745.6998715822701 W per hp_i and 1000 W per kw. 1 mechanical hp = 550 ft·lbf/s = 745.699 871 582 270 W exactly (NIST SP 811); 1 metric hp (PS) = 75 kgf·m/s = 735.498 75 W exactly (DIN 66036); 1 electrical hp = 746 W exactly (NEMA); 1 boiler hp ≈ 9 809.5 W (ASME).
How to use this calculator
Enter a value, pick the unit you have under "From", then choose the unit you want under "To". Results update instantly. Use mechanical hp (hp(I)) for US car specs, metric hp (PS, ch, CV) for European specs, electrical hp for AC motors, and kilowatts (kW) for SI engineering or EU vehicle plates.
How the calculation works
Every unit converts via a single intermediate value in watts (1 W = 1 J/s = 1 kg·m²/s³). Factors are exact under the SI definitions and the 1959 International Yard and Pound Agreement: 1 mechanical hp = 550 ft·lbf/s = 745.699 871 582 270 W exactly (NIST SP 811); 1 metric hp (PS) = 75 kgf·m/s = 735.498 75 W exactly (DIN 66036, using standard gravity g₀ = 9.806 65 m/s²); 1 electrical hp = 746 W exactly (NEMA / IEEE 100); 1 boiler hp = 33 475 BTU/h ≈ 9 809.5 W (ASME PTC 4).
Worked example
A 200 hp car engine (US spec) → kilowatts: 200 × 745.69987158 ≈ 149.14 kW. → metric horsepower: 149 139.97 ÷ 735.49875 ≈ 202.77 PS. That is why a "200 hp" American car is usually badged as "203 PS" in Germany or "203 ch" in France — the underlying engine power is the same, but mechanical hp and metric PS differ by about 1.4 %.
Frequently asked questions
What is the difference between mechanical hp and metric hp (PS)?
Mechanical horsepower (also called imperial or hp(I)) is defined as 550 foot-pounds-force per second, giving 745.699 871 582 270 W exactly. Metric horsepower (called PS in Germany, ch in France, CV in Italy, pk in the Netherlands) is defined as 75 kilogram-force·metres per second, giving 735.498 75 W exactly. They differ by about 1.4 % — 1 mechanical hp = 1.013 87 PS. American and British car specs use hp; almost all of continental Europe uses PS or its language-specific equivalent.
How many kilowatts is 1 horsepower?
It depends which horsepower. 1 mechanical hp = 0.745 699 871 582 270 kW (US car specs). 1 metric hp (PS) = 0.735 498 75 kW (European car specs). 1 electrical hp = 0.746 kW exactly (US motor nameplates). For quick mental maths, "1 hp ≈ ¾ kW" is close enough for both — so a 100 hp engine is roughly 75 kW, and a 100 kW motor is roughly 134 hp.
What is electrical horsepower and why is it different?
Electrical horsepower (hp(E)) is fixed at exactly 746 W by NEMA and IEEE 100, used on US electric motor nameplates. The reason it differs from mechanical hp (745.699 87 W) is purely historical: motor manufacturers rounded the conversion for simpler maths. The difference is tiny (≈ 0.04 %) so for practical purposes a 5 hp motor is 3.73 kW regardless of which definition you use. Use hp(E) only when the nameplate explicitly says so; otherwise mechanical hp is the default.
What is boiler horsepower and where is it used?
Boiler horsepower (bhp) is a thermal output unit, not a mechanical one. ASME defines 1 bhp as the heat required to evaporate 34.5 pounds of water per hour at 212 °F into steam at atmospheric pressure — which works out to 33 475 BTU/h or approximately 9 809.5 W. It is about 13 times larger than mechanical hp, so a 100 bhp boiler outputs roughly 981 kW of heat. You will see this on US and Canadian boiler plates; metric and modern specs use kW directly.
How do I convert kW to hp on my car?
European registration documents usually give engine power in kW. To convert to mechanical hp (the number Americans use), multiply kW by 1.341 02. To convert to metric hp (PS, the number Germans use), multiply kW by 1.359 62. Example: a 100 kW engine = 134.10 hp (mechanical) = 135.96 PS. A 150 kW EV motor = 201.15 hp = 203.94 PS. EU regulation requires kW on the V5 / Fahrzeugschein; PS or hp is courtesy marketing.
Why does a "metric system" use horsepower at all?
Metric horsepower (PS) was defined in 19th-century Germany as a "metric-friendly" replacement for the British imperial hp — using kilograms and metres instead of pounds and feet, but still anchored on the idea of one horse lifting a heavy load one metre in one second. The watt was made the SI unit of power in 1960, but PS stuck on car spec sheets across Europe because consumers were used to it. EU vehicle homologation forms now require kW, with PS shown as a secondary figure.
What is BTU/h and how does it relate to horsepower?
BTU per hour (British Thermal Units per hour) is a thermal power unit used for HVAC, heating, and refrigeration. 1 BTU/h ≈ 0.2931 W. A typical home air-conditioner might be rated 12 000 BTU/h, which is about 3 517 W or 4.72 mechanical hp. Boiler hp is defined as 33 475 BTU/h, which is why boiler horsepower is so much larger than mechanical horsepower — they describe entirely different things (heat output vs mechanical shaft power), even though both are valid "horsepower" units.