Horsepower to Watts Converter
Convert mechanical horsepower to watts — one hp is 745.7 W. Results update as you type; exact factors shown.
One horsepower (mechanical) is 745.6999 watts — see the exact factor, not a rounded rule of thumb.
How the horsepower to watts converter works
Power converts through the watt. Mechanical horsepower is 550 ft·lbf/s = 745.6999 W; metric horsepower (PS, used in European car specs) is 735.4988 W. Air-conditioner capacities are quoted in kW, BTU/h (1 W = 3.412 BTU/h) or tons of refrigeration (3.517 kW).
The US uses customary units (US gallon, short ton, °F) in daily life; NIST SP 811 gives the exact SI factors.
Common power conversions
| From | To | Units |
|---|---|---|
| 0.5 hp | 372.8499 W | horsepower (mechanical) to watts |
| 1 hp | 745.6999 W | horsepower (mechanical) to watts |
| 5 hp | 3,728.4994 W | horsepower (mechanical) to watts |
| 10 hp | 7,456.9987 W | horsepower (mechanical) to watts |
| 25 hp | 18,642.4968 W | horsepower (mechanical) to watts |
| 50 hp | 37,284.9936 W | horsepower (mechanical) to watts |
| 100 hp | 74,569.9872 W | horsepower (mechanical) to watts |
| 150 hp | 111,854.9807 W | horsepower (mechanical) to watts |
| 200 hp | 149,139.9743 W | horsepower (mechanical) to watts |
| 300 hp | 223,709.9615 W | horsepower (mechanical) to watts |
| 500 hp | 372,849.9358 W | horsepower (mechanical) to watts |
| 1,000 hp | 745,699.8716 W | horsepower (mechanical) to watts |
Units in this converter and their exact factors
| Unit | Symbol | One unit in watts |
|---|---|---|
| watt | W | 1 watt |
| kilowatt | kW | 1,000 watt |
| megawatt | MW | 1,000,000 watt |
| horsepower (mechanical) | hp | 745.6998715823 watt |
| metric horsepower (PS) | PS | 735.49875 watt |
| BTU per hour | BTU/h | 0.29307107 watt |
| ton of refrigeration | TR | 3,516.8528421 watt |
FAQFrequently asked questions about power conversion
How many watts in a horsepower?
745.6999 W for mechanical horsepower.
Is metric horsepower different?
Yes — PS is 735.5 W, about 1.4% less.
Where does 745.7 come from?
James Watt defined it as 33,000 foot-pounds per minute, from measurements of drayhorses lifting loads.
What is 150 hp in kW?
111.9 kW.
Do horses produce one horsepower?
Briefly they exceed it; sustained output is closer to 0.5 hp. Watt chose a generous figure deliberately.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Institute of Standards and Technology (NIST) — United States's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.