Conversion factor
1 W = 0.001341 hp
and 1 hp = 745.7 W
The formula
horsepower = watts × 0.001341
Worked example. To convert 100 W, multiply by 0.001341: 100 × 0.001341 = 0.134102 hp.
Watts to Horsepower conversion table
| watts (W) | horsepower (hp) |
|---|---|
| 100 | 0.134102 |
| 500 | 0.670511 |
| 745.7 | 1 |
| 1000 | 1.34102 |
| 5000 | 6.70511 |
| 10000 | 13.4102 |
| 50000 | 67.0511 |
| 75000 | 100.577 |
| 100000 | 134.102 |
About watts and horsepower
There is more than one horsepower. Mechanical horsepower, used in the UK and US, is 745.6998716 watts. Metric horsepower, written PS or CV and standard across continental Europe, is 735.49875 watts, about 1.4% smaller. A car advertised at 150 PS in Germany is around 148 hp in Britain, describing the same engine.
The unit dates from James Watt's marketing of steam engines in the 1780s. He estimated the sustained output of a working horse turning a mill wheel and priced his engines against it. The watt was named after him a century later, which is why the two units are so entangled in engineering.
You will also meet bhp, brake horsepower, which is measured at the engine flywheel before losses through the gearbox and drivetrain. Wheel horsepower is typically 10 to 15% lower. When comparing figures, check they were measured the same way — the power converter covers both horsepower definitions alongside BTU/h and kilowatts.
Need other units?
The full power converter handles every unit in this family.
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Frequently Asked Questions
- How many watts are in one horsepower?
- 745.7 watts for mechanical horsepower, the figure used in the UK and US. Metric horsepower, written PS, is 735.5 watts.
- How do I convert kW to hp?
- Multiply kilowatts by 1.341 for mechanical horsepower, or by 1.360 for metric horsepower (PS). A 100 kW engine is 134 hp or 136 PS.
- What is the difference between hp, bhp and PS?
- hp and bhp are both mechanical horsepower at 745.7 W; bhp specifies that the measurement was taken at the flywheel before drivetrain losses. PS is metric horsepower at 735.5 W, about 1.4% smaller.
- Why is horsepower still used for engines?
- Convention and familiarity. Kilowatts are the SI unit and appear on European documentation, but buyers have decades of intuition for horsepower figures, so manufacturers keep quoting both.
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