HP to kW Converter
Convert horsepower to kilowatts for US motors, vehicles, and engineering specs.
How It Works
Formula: hp to kW = value × 0.745699872
Example: 1 hp = 0.7457 kW
Note: 1 mechanical horsepower equals 0.7457 kilowatts, the conversion for US motors and vehicles.
Common Uses
Quick Conversion Table
| hp | kW |
|---|---|
| 1 | 0.7457 |
| 5 | 3.7285 |
| 10 | 7.457 |
| 50 | 37.285 |
| 100 | 74.57 |
| 500 | 372.8499 |
Rounding Rule
Rounded to 4 decimal places
Error Margin
±0.0001 kW
Precision Guidance
For vehicles, round to 2 decimals. For engineering, keep 3-4 decimals.
Common Mistakes
Mechanical horsepower (0.7457 kW) differs from metric horsepower/PS (0.7355 kW). Confirm which a spec uses.
Frequently Asked Questions
What is 1 hp in kW?
1 mechanical horsepower equals 0.7457 kilowatts (1 hp = 0.7456999 kW).
How do I convert hp to kW?
Multiply the horsepower value by 0.7457. For example, 100 hp × 0.7457 = 74.57 kW.
Is this mechanical or metric horsepower?
This uses mechanical (imperial) horsepower (0.7457 kW). Metric horsepower (PS) is 0.7355 kW.
Why do EVs use kW?
Electric vehicles rate motors in kilowatts, the SI unit, while US cars often cite horsepower for comparison.
Deep Dive Guide
HP to KW: Converting Horsepower to Kilowatts for US Cars and EVs
Convert hp to kw for US car specs, truck ratings, and EV motors. 1 mechanical horsepower equals 0.7457 kW, the standard American automakers use.
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Exact Constants & Authoritative Sources
Every conversion on this page uses the fixed, internationally agreed constants below — drawn from NIST and the SI Brochure. No values are estimated or rounded as if exact. See the full list on our Sources & Standards page.
- EXACT1 mechanical horsepower (hp) = 745.6998715823 watts (exact, 550 ft·lbf/s)
- EXACT1 British thermal unit, IT (Btu) = 1055.05585262 joules (exact)
- EXACT1 Btu/h = 0.293071070172 watts (exact, Btu ÷ 3600 s)
- EXACT1 watt (W) = 1 joule per second (definition)
Common Pitfalls & How to Avoid Them
Mechanical hp vs. metric hp
Mechanical hp = 745.7 W. Metric (PS) hp = 735.5 W and electrical hp = 746 W. Engine specs may use any of these; always check which.
Btu IT vs. thermochemical
UnitFig uses the IT Btu (1055.05585262 J). The thermochemical Btu (1054.35 J) is ~0.07% smaller and used in some chemistry contexts — keep them separate.
A unit-conversion reference site has no manufacturer-specific or device calibration parameters, so "layered tuning" does not apply here. The only real error-handling is input validation: the converter rejects non-numeric, empty, or out-of-range entries and shows a clear message, then falls back to exact constants above. No estimated or rounded figures are ever presented as exact.
Authoritative sources for this page
- NIST (U.S. National Institute of Standards and Technology) — NIST SP 330 — The International System of Units (SI), 2019 edition
- BIPM (International Bureau of Weights and Measures) — SI Brochure — The International System of Units (9th edition)
Last Updated 2026 | This converter was reviewed for accuracy