Horsepower Converter – hp, PS, Electrical & Boiler HP Explained
"Horsepower" is one of the most recognized power units in the world — yet the word covers at least four distinct definitions used in different industries and regions. This free Horsepower Converter lets you translate between Mechanical HP (hp), Metric HP (PS / CV), Electrical HP, and Boiler HP (BHP), as well as standard units like watts, kilowatts, megawatts, BTU/h, and foot-pounds per second.
The Four Types of Horsepower
Understanding which horsepower definition applies to your use case is the first step to accurate conversion:
- Mechanical Horsepower (hp) — The North American and UK automotive standard. Defined by James Watt as
550 ft·lbf/s, exactly745.699872 Wper the IEEE definition. Engine specs in the US always use mechanical HP. - Metric Horsepower (PS / CV / hk) — The European and Asian automotive standard. Defined as
75 kgf·m/s = 735.49875 W. One mechanical HP is approximately 1.014 PS, so a European car rated at 200 PS produces roughly 197 US hp. - Electrical Horsepower (hp) — Used on electric motor nameplates (NEMA/IEC standard). Defined as exactly
746 W— slightly higher than mechanical HP. If your electric motor's nameplate says "5 hp," it is rated at 3,730 W. - Boiler Horsepower (BHP) — An industrial unit for steam boilers. One boiler HP equals the energy required to evaporate 34.5 lb of water per hour at 212 °F, equivalent to
9,809.5 W— about 13.15 mechanical HP. It is used in ASME boiler specifications and industrial plant engineering.
Conversion Formula
All conversions in this tool follow a two-step approach using the Watt as the common base:
- Multiply the input by the source unit's to-Watt factor to obtain the equivalent power in Watts.
- Divide the Watt value by the target unit's to-Watt factor to get the final result.
For example, to convert 200 mechanical HP to kilowatts:
200 × 745.699872 W/hp ÷ 1,000 W/kW = 149.14 kW
Practical Use Cases
Automotive Engineering
When comparing a US car (rated in mechanical HP) with a European model (rated in PS), divide the PS figure by 1.01387 to obtain the mechanical HP equivalent. This is especially important when analyzing sports-car dyno sheets or homologation documents.
Electric Motor Sizing
Electric motors in North America are labeled in electrical HP (= 746 W each). To calculate the required electrical input power, divide the shaft output in electrical HP by the motor's efficiency. For example, a 10 hp motor at 92% efficiency draws about 10 × 746 W ÷ 0.92 ≈ 8,109 W from the supply.
HVAC and Industrial Boiler Specifications
Boiler HP is common on data sheets for commercial steam boilers, autoclaves, and laundry equipment. Converting to kW or BTU/h allows direct comparison with electric heating elements or gas-fired heaters that use SI or Imperial thermal units.
Batch Comparison of Engine Lineups
Use Batch Mode to paste a column of horsepower values (e.g., every trim level of a model year) and convert all of them to kilowatts at once — ideal for generating localized spec sheets.
Quick Reference: 1 Mechanical HP in Common Units
| Unit | Value |
|---|---|
| Watts (W) | 745.70 W |
| Kilowatts (kW) | 0.7457 kW |
| Metric HP (PS) | 1.0139 PS |
| Electrical HP | 0.9996 hp(E) |
| Boiler HP | 0.0760 BHP |
| BTU/hour | 2,544.43 BTU/h |
| Foot-pound/sec | 550 ft·lb/s |
Tips for Accurate Results
- Always confirm which horsepower variant your source document uses. Car datasheets from the US use mechanical HP; European sheets use PS or kW.
- For electric motor calculations, use Electrical HP — not mechanical HP — to match the nameplate rating.
- Boiler HP should be used only for steam-generating equipment. Do not confuse it with brake horsepower (bhp), which is a test-bench measure of mechanical HP.
- Set decimal places to 6 or more for engineering-grade calculations; 2 is sufficient for everyday automotive comparisons.
About the Tool
This converter runs entirely in your browser — no data is sent to any server. Conversion factors are sourced from IEEE, SI, NEMA, and ASME standards. The Show All Units toggle reveals a grouped breakdown of the input value expressed in every supported unit simultaneously, making it easy to cross-reference specifications across different systems at a glance.