Convert Horsepower to Watts
Horsepower to watts is the conversion you need when an engine or motor is rated in horsepower but you want its output in the metric power unit. One horsepower is approximately 745.6998715822702 watts, so the watt number always comes out much larger. This is the mechanical (imperial) horsepower used for US and UK car engines.
Horsepower (mechanical) to Watts conversion table
| Horsepower (mechanical) (hp) | Watts (W) |
|---|---|
| 1 | 745.699872 |
| 2 | 1,491.399743 |
| 3 | 2,237.099615 |
| 5 | 3,728.499358 |
| 10 | 7,456.998716 |
| 20 | 14,913.997432 |
| 50 | 37,284.993579 |
| 100 | 74,569.987158 |
| 500 | 372,849.935791 |
| 1,000 | 745,699.871582 |
The formula
To convert horsepower to watts, multiply the number of horsepower by 745.6998715822702:
watts = horsepower × 745.6998715822702
A worked example
Say you have a 200-horsepower engine and want its output in watts:
200 × 745.6998715822702 = 149,139.97 W
So a 200-horsepower engine puts out about 149,140 watts.
Why it's an approximation
The horsepower here is the mechanical (imperial) horsepower, defined as 550 foot-pounds-force per second. That definition comes from imperial units that don't divide evenly into the watt, so converting gives a long, non-terminating number — about 745.6998715822702 watts. That's why the figure stays approximate no matter how many decimals you keep. Note this is a bit larger than the metric horsepower (PS) used on European spec sheets, which is about 735.5 watts.
When you'll use it
Reading US or UK car engine ratings in horsepower and translating them into the metric watts used in physics, electrical work, and international specs.
Frequently asked questions
How many watts are in one horsepower?
About 745.6998715822702 watts. It's a rounded figure — the mechanical horsepower doesn't convert to a clean, terminating number of watts, so this long value is the practical one to use.
Is this the same horsepower Europe uses on spec sheets?
No. This is the mechanical (imperial) horsepower, common on US and UK car engines. European spec sheets usually quote metric horsepower (PS or CV), which is about 1.4% smaller — roughly 735.5 watts. Check which one a rating means before converting.
Is the horsepower to watts conversion exact?
No. The mechanical horsepower is defined from imperial units that don't line up cleanly with the watt, so 745.6998715822702 is a rounded value. More decimal places give you more precision if you need it.