Horsepower and kilowatts
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.
A kilowatt is 1,000 watts. Car and motorcycle engine power in Europe, EV chargers, heat pumps and home solar systems use kW.
Worked example
Convert 300 hp: 300 × 0.7456998716 = 223.7099615, so 300 horsepower is 223.7099615 kilowatts. Likewise 100 hp = 74.56998716 kW.
Estimating in your head
Multiply by 0.75 for a quick figure; it is off by about 0.6%. For 300 hp that gives 225 kW, against 223.71 exactly.
Going the other way
To convert kilowatts to horsepower, divide by 0.7456998716 (or multiply by 1.3410220896). The swap button between the boxes opens that page.
How this works
kW = hp × 0.7456998716
1 hp = ≈ 745.6998716 W and 1 kW = 1,000 W, both by definition, so the factor is their ratio: 0.7456998716 (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 kilowatts are in a mechanical horsepower?
1 mechanical horsepower = 0.7456998716 kilowatts. 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 horsepower to kilowatts?
Multiply by 0.7456998716. For example, 100 hp × 0.7456998716 = 74.56998716 kW.
What is 1,000 hp in kilowatts?
1,000 hp = 745.6998716 kW. 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/hp-to-kw/