Watts and horsepower
The watt is the SI unit of power: one joule per second. Light bulbs, appliances, chargers and solar panels are rated in watts.
Mechanical horsepower is exactly 550 foot-pounds-force per second: about 745.7 watts. Car, boat and lawnmower engines in the US and UK, and electric motors, are rated in hp.
Worked example
Convert 1,500 W: 1,500 × 0.00134102209 = 2.011533134, so 1,500 watts is 2.011533134 horsepower. Likewise 1,000 W = 1.34102209 hp.
Estimating in your head
Divide by 750 for a quick figure; it is off by about 0.6%. For 1,500 W that gives 2 hp, against 2.01153 exactly.
Going the other way
To convert horsepower to watts, divide by 0.00134102209 (or multiply by 745.699871582). The swap button between the boxes opens that page.
How this works
hp = W × 0.00134102209
1 W = 1 W and 1 hp = ≈ 745.6998716 W, both by definition, so the factor is their ratio: 0.00134102209 (rounded here; the page uses the full value). Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many horsepower are in a watt?
1 watt = 0.00134102209 horsepower. The factor is exact by definition but has endless decimals, so it is shown rounded; the page uses the full value.
How do I convert watts to horsepower?
Multiply by 0.00134102209. For example, 1,000 W × 0.00134102209 = 1.34102209 hp.
What is 10,000 W in horsepower?
10,000 W = 13.4102209 hp. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically
- NIST SP 811 Appendix B.9 — Factors for units listed by kind of quantity
- Wikipedia — Horsepower
Reviewed Oct 17, 2026 · test vectors fixtures/units/power/watts-to-hp/