Convert Watts to Horsepower
Watts to horsepower is the conversion you need when an engine or motor is rated in metric watts but you think in horsepower — the number US and UK car specs use. This page uses mechanical (imperial) horsepower, hp. One watt is approximately 0.00134102 horsepower, so the horsepower figure always comes out much smaller.
Watts to Horsepower (mechanical) conversion table
| Watts (W) | Horsepower (mechanical) (hp) |
|---|---|
| 1 | 0.001341 |
| 2 | 0.002682 |
| 3 | 0.004023 |
| 5 | 0.006705 |
| 10 | 0.01341 |
| 20 | 0.02682 |
| 50 | 0.067051 |
| 100 | 0.134102 |
| 500 | 0.670511 |
| 1,000 | 1.341022 |
The formula
To convert watts to mechanical horsepower, multiply the number of watts by 0.00134102:
horsepower = watts × 0.00134102
A worked example
Say a motor is rated at 745.7 watts and you want it in horsepower:
745.7 W ≈ 1 hp
So about 745.7 watts is roughly one mechanical horsepower.
Why it's an approximation
Mechanical horsepower isn't defined from the watt — it comes from an old imperial measure of 550 foot-pounds of work per second. When you line that up against the watt, the numbers don't divide evenly, so one watt works out to approximately 0.00134102 hp. More decimal places give you more precision if you need it, but the figure stays approximate.
One thing to watch: there are two horsepowers. This page uses mechanical (imperial) horsepower, hp, the one on US and UK car spec sheets. European spec sheets often use metric horsepower (PS), which is a slightly different, smaller unit — the two differ by about 1.4 percent, so check which one a rating means before you compare.
When you'll use it
Comparing an engine or motor rated in watts against the horsepower figures you're used to on US and UK cars, tools, and pumps, or sanity-checking a spec sheet that mixes metric and imperial power units.
Frequently asked questions
How many horsepower are in a watt?
About 0.00134102 hp. It's a rounded figure — the exact value runs on past several decimal places, so 0.00134102 is the practical number to use.
Which horsepower is this — there seem to be two?
This is mechanical (imperial) horsepower, hp, the one used on US and UK car spec sheets, where 1 hp is about 745.7 watts. Europe often quotes metric horsepower (PS), which is slightly smaller — the two differ by roughly 1.4 percent.
Is the watts to horsepower conversion exact?
No. Mechanical horsepower is defined from foot-pounds per second, which doesn't divide evenly into watts, so the factor 0.00134102 is rounded for everyday use.