Horsepower to Kilowatt Formula
kW = hp(mech) × 0.7456998715822702
Conversion factors follow SI relationships published by BIPM and IEC, where those standards apply.
Derived from 1 hp = 550 ft·lbf/s and 1 ft·lbf/s = 1.3558179483314004 W (NIST). Reverse: hp = kW × 1.341022089595.
Horsepower to Kilowatt Converter
Quick Answer
1 hp = 0.7457 kW
Formula: Kilowatt = Horsepower x 0.7457
Quick values
Sources
- NIST Special Publication 811 — Guide for the Use of the International System of Units (SI), including appendix conversion factors.
- BIPM SI Brochure — Definitions of the pascal, watt, and other SI derived units.
- NIST SI units of power — Watt = joule per second; kilowatt = 10³ W.
Worked examples
- 1 mechanical horsepower: 1 × 0.7456998715822702 = 0.74570 kW
- 10 hp shop compressor: 10 × 0.7456998715822702 = 7.4570 kW
- 200 hp automobile engine: 200 × 0.7456998715822702 = 149.14 kW
What is mechanical horsepower to kilowatts?
Mechanical horsepower is 550 ft·lbf/s, equal to 0.74569987 kW. Electrical horsepower is 0.746 kW and metric horsepower (PS) is 0.73549875 kW.
FormulakW = hp(mech) × 0.7456998715822702
Key conversions
- 1 hp(mech) = 0.74569987 kW
- 1 hp(E) = 0.746 kW
- 1 PS = 0.73549875 kW
How many kilowatts is 1 horsepower?
Mechanical horsepower — the definition this calculator uses — is 550 foot-pounds per second. In SI that is 745.6998715822702 watts, or 0.7456998715822702 kilowatts. A 150 hp gasoline engine is therefore 111.85 kW at the same shaft condition the rating was measured.
Nameplates are not interchangeable across horsepower conventions. Electrical (NEMA) horsepower is 746 W exactly. Metric horsepower (DIN PS, French CV) is 75 kgf·m/s = 735.49875 W. If a European motor says “11 kW (15 PS)”, convert from metric horsepower, not from SAE mechanical hp.
Category hub: Power Conversion · Conversion charts · Conversion formulas
Which horsepower is on the nameplate?
Use mechanical hp (this page) for SAE net engine ratings and most US pump curves. Use 746 W/hp for NEMA motor nameplates quoted in electrical horsepower. Use 735.49875 W/hp when the sheet says PS, CV, or “metric hp”. Boiler horsepower is a different quantity (~9.81 kW) and is not a shaft-power unit.
| Convention | Watts per hp | Kilowatts per hp | Where it appears |
|---|---|---|---|
| Mechanical (hp) | 745.699872 | 0.745700 | SAE engines, US pumps |
| Electrical (hp(E)) | 746 | 0.746 | NEMA motors |
| Metric (PS / hp(M)) | 735.49875 | 0.735499 | DIN / EU nameplates |
Horsepower conventions versus the SI watt
Horsepower to Kilowatt Conversion Table
Mechanical-horsepower ratings converted to kilowatts
| Horsepower (hp) | Kilowatt (kW) |
|---|---|
| 1 hp | 0.7457 kW |
| 5 hp | 3.7285 kW |
| 10 hp | 7.457 kW |
| 15 hp | 11.1855 kW |
| 25 hp | 18.6425 kW |
| 50 hp | 37.285 kW |
| 75 hp | 55.9275 kW |
| 100 hp | 74.57 kW |
| 150 hp | 111.855 kW |
| 200 hp | 149.14 kW |
| 250 hp | 186.425 kW |
| 400 hp | 298.28 kW |
| 1000 hp | 745.7 kW |
Table uses mechanical hp (550 ft·lbf/s). Electrical and metric horsepower differ by about 0.04% and 1.4%.
Browse all conversion charts → · Browse conversion formulas →
Practical use cases for Horsepower to Kilowatt
Motor and Drive Selection
Nameplates mix horsepower and kilowatts. Specifying a replacement motor requires converting so the electrical supply and mechanical load match.
Generator and Plant Sizing
Prime-mover ratings may be in horsepower while electrical output is in kW or kVA. Planners convert before comparing mechanical and electrical capacity.
HVAC Equipment
Fans, pumps, and chillers are cataloged in horsepower, kW, or tons of refrigeration. Designers convert to the unit used on the project schedule.
Automotive and Marine
Engine output is advertised in horsepower in some markets and kilowatts in others. Comparing vehicles requires a consistent power unit.
Renewable Energy
Inverter and turbine ratings are in kW or MW while some legacy documents still use horsepower. Conversion keeps interconnection studies consistent.
Workshop and Tooling
Machine-tool spindles and air compressors are often labeled in horsepower. Electrical planning converts that rating to kW for feeder and breaker sizing.
Horsepower to Kilowatt FAQs
Common questions about converting horsepower to kilowatt.
Is 1 hp exactly 0.746 kW?
Only if the rating is electrical horsepower (746 W). Mechanical horsepower is 0.74569987 kW. Metric horsepower is 0.73549875 kW. The 0.746 kW rule of thumb is the electrical convention, not the shaft definition James Watt used (550 ft·lbf/s).
How do I convert horsepower to kilowatts for an electric motor?
If the motor is labeled in NEMA horsepower, multiply by 0.746. If it is labeled in mechanical hp, use 0.7457. Output power is still η × input electrical kW; do not treat nameplate hp as the electrical draw. Input kW = (hp × 0.746) / efficiency for a first-pass feeder size.
Why is 100 hp advertised as 74.6 kW in one catalog and 73.5 kW in another?
74.57 kW is 100 mechanical hp. 73.55 kW is 100 metric hp (PS). Confirm the standard on the datasheet before comparing engines or motors from different markets.
Does kilowatt-hour enter this conversion?
No. Kilowatts are power (joules per second). Kilowatt-hours are energy. Converting hp to kWh requires a time: kWh = hp × 0.7457 × hours. That is a different calculator.
What factor does this site use for hp → kW?
Mechanical horsepower: 1 hp = 745.6998715822702 W. That matches 550 ft·lbf/s with the international foot-pound-force. Swap to the kilowatts-to-horsepower page for the inverse, or use the watts-to-horsepower page when the input is in watts instead of hp.
Charts and printable PDF
Use the matching horsepower / kilowatt chart when you need a printable table or offline reference.
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