Power Conversion Calculator
Two Different Horsepowers, and Both Are in Use
When a European manufacturer quotes 150 PS and an American one quotes 150 hp, those are not the same engine. Mechanical horsepower is 745.6998715822702 watts; metric horsepower (PS, or Pferdestärke) is 735.49875 watts. The gap is about 1.4% — small enough to be ignored casually, large enough to matter in a spec comparison or a homologation document. This converter treats them as the distinct units they are.
The Formula
Power is the rate of energy transfer, and the watt — one joule per second — is the base every unit here pivots through:
(Factors are relative to 1 watt)
Converting 200 hp to kilowatts is 200 × 745.6998715822702 ÷ 1000 = 149.13997432 kW.
The Factors
| Unit | Code | Watts per unit | Basis |
|---|---|---|---|
| Watts | w | 1 | SI: 1 J/s |
| Kilowatts | kw | 1000 | SI multiple |
| Megawatts | mw | 1000000 | SI multiple |
| Horsepower (Mechanical) | hp | 745.6998715822702 | 550 ft·lbf/s |
| Metric Horsepower (PS) | ps | 735.49875 | 75 kgf·m/s |
| BTU/Hour | btu_hr | 0.29307107017222222 | 1 BTU per 3600 s |
| Foot-Pounds/Second | ftlb_s | 1.3558179483314 | 1 ft·lbf per second |
Mechanical horsepower's odd factor traces back to its definition as 550 foot-pounds per second: 550 × 1.3558179483314 = 745.6998715822702 W exactly.
Horsepower and Kilowatts
The conversion that gets run most, in both directions:
| Horsepower | Kilowatts |
|---|---|
| 1 | 0.74569987 |
| 100 | 74.56998716 |
| 150 | 111.85498074 |
| 200 | 149.13997432 |
| 300 | 223.70996147 |
| 500 | 372.84993579 |
| Kilowatts | Horsepower |
|---|---|
| 1 | 1.34102209 |
| 50 | 67.05110448 |
| 100 | 134.10220896 |
| 150 | 201.15331344 |
| 200 | 268.20441792 |
Full Cross-Reference
| 1 of… | Watts | Kilowatts | hp | PS | BTU/hr |
|---|---|---|---|---|---|
| Watt | 1 | 0.001 | 0.00134102 | 0.00135962 | 3.41214163 |
| Kilowatt | 1000 | 1 | 1.34102209 | 1.35962162 | 3412.14163313 |
| Megawatt | 1000000 | 1000 | 1341.0220896 | 1359.6216173 | 3412141.63313 |
| Horsepower (Mechanical) | 745.69987158 | 0.74569987 | 1 | 1.01386967 | 2544.43357764 |
| Metric Horsepower (PS) | 735.49875 | 0.73549875 | 0.98632007 | 1 | 2509.62590599 |
| BTU/Hour | 0.29307107 | 0.00029307 | 0.00039301 | 0.00039847 | 1 |
| Foot-Pound/Second | 1.35581795 | 0.00135582 | 0.00181818 | 0.0018434 | 4.62624287 |
Where the Distinction Counts
- Vehicle and engine specs — comparing a European PS rating against a North American hp rating, or either against a kW figure on an EV.
- HVAC equipment — air conditioners rated in BTU/hour against heat pumps rated in kilowatts. The 3412.14163313 BTU/hr per kW factor is the bridge.
- Electric motors — industrial motors are nameplated in hp in some markets and kW in others, and drive sizing depends on getting it right.
- Generators and plant capacity — output in megawatts translated to horsepower for mechanical comparison.
- Mechanical work rate — foot-pounds per second appearing in older engineering texts alongside modern watt figures.
How to Use This Calculator
- Enter the power figure in the Value field.
- Select the source unit in the first dropdown — check whether a horsepower figure is mechanical hp or metric PS before choosing.
- Select the target unit in the second dropdown.
- Press Calculate. The breakdown lists both watt factors and the division.
Related Calculations
Power sustained over time gives energy — the Energy Conversion Calculator covers joules, kWh and BTU. For data throughput rather than electrical power, see the Data Transfer Rate Converter.