Convert Horsepower to Kilowatts – Power Converter
This converter translates a single value in horsepower (hp) to the corresponding value in kilowatts (kW). It uses standard SI relationships and calls out the common horsepower variants so you can choose the correct factor for your context.
Use the mechanical horsepower to kilowatt factor for most engineering and automotive conversions. For tasks requiring regulatory compliance, specification matching, or precise loss accounting, check the nameplate definitions and local standards before applying rounded values.
Interactive Converter
Convert between horsepower and kilowatt with precision rounding.
Quick reference table
| Horsepower | Kilowatt |
|---|---|
| 1 hp | 0.746 kW |
| 5 hp | 3.729 kW |
| 10 hp | 7.457 kW |
| 25 hp | 18.643 kW |
| 50 hp | 37.285 kW |
| 100 hp | 74.57 kW |
Methodology
Power is a physical quantity measured in watts (W) in the International System of Units (SI). Kilowatt is a multiple of watt (1 kW = 1000 W). Horsepower is a non-SI unit historically defined in several ways; the converter maps horsepower to watts and then to kilowatts using established factors.
Primary conversion uses the mechanical (imperial) horsepower definition: 1 mechanical horsepower = 745.699872 watts. Where applicable, a metric or 'PS' definition is provided: 1 metric horsepower (often written as PS or hp (metric)) = 735.49875 watts. Always confirm which hp variant your source uses.
Worked examples
150 hp (mechanical) → 150 × 0.745699872 = 111.8549808 kW (report as 111.85 kW when rounded to two decimals)
10 hp (metric/PS) → 10 × 0.73549875 = 7.3549875 kW (report as 7.355 kW to three decimals)
1 hp (mechanical) → 0.745699872 kW; 1 kW → 1.34102209 mechanical hp (inverse factor)
Further resources
Expert Q&A
Which horsepower definition should I use?
Use the horsepower definition that matches your source. For engineering and many automotive contexts use mechanical (imperial) horsepower (1 hp = 745.699872 W). If a manufacturer lists 'PS' or 'metric hp', use the metric factor (1 PS = 735.49875 W). If the source is unclear, consult the equipment nameplate or specification sheet.
How many decimal places should I report?
Choose precision according to purpose. For specification sheets and procurement, two to three significant digits after the decimal are common (for example, 111.85 kW). For instrumentation or calculations feeding other models, preserve full precision internally and round only for presentation.
Does this conversion account for mechanical or electrical losses?
No. This converter performs a purely mathematical unit conversion between hp and kW. It does not include losses or efficiency factors. When comparing engine hp to motor kW, include appropriate efficiency or transmission losses separately.
Are there regulatory or standards considerations?
Yes. Use the SI-backed kilowatt values for regulatory reporting where required. For traceable measurements and documentation, follow guidance from recognized standards bodies and maintain measurement uncertainty records if results are used for compliance or safety.
Can I convert back from kW to hp?
Yes. Use the inverse factor: mechanical hp = kW ÷ 0.745699872 (approximately kW × 1.34102209). Be sure to select the correct hp variant when converting back.
Sources & citations
- NIST Guide for the Use of the International System of Units (SI) — https://www.nist.gov/pml/special-publication-811
- ISO 80000-1 Quantities and units — https://www.iso.org/standard/30669.html
- IEEE Standards and Unit Practices — https://standards.ieee.org
- Occupational Safety and Health Administration (OSHA) — https://www.osha.gov