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 UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
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 Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.