How to Convert Watts to Horsepower (W to hp)
Power conversions help compare car engines in hp and kW, and air-con units rated in BTU/h against their electrical draw in watts. This guide shows how to convert watts into horsepower by hand, with examples and a quick-reference table.
The conversion
To convert watts to horsepower, multiply the value by 0.0013410221. To go the other way, divide by the same number (or multiply by 745.699872). For a quick estimate, multiply by about 0.0013.
Horsepower = watts × 0.0013410221
Worked examples
- 3 W = 0.004023 hp
- 12.5 W = 0.016763 hp
- 75 W = 0.100577 hp
Watts to Horsepower table
| Watts | Horsepower |
|---|---|
| 1 W | 0.001341 hp |
| 2 W | 0.002682 hp |
| 5 W | 0.006705 hp |
| 10 W | 0.01341 hp |
| 20 W | 0.02682 hp |
| 25 W | 0.033526 hp |
| 50 W | 0.067051 hp |
| 100 W | 0.134102 hp |
| 250 W | 0.335256 hp |
| 500 W | 0.670511 hp |
| 1,000 W | 1.341 hp |
Common questions
Is W to hp exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Horsepower to Watts converter.
Mistakes to avoid
Dropping the units
A bare number without a unit is easy to misread later. Always write the unit with the result.
Forgetting squared and cubed units
Area and volume factors are the length factor squared or cubed, so 1 m² is about 10.76 sq ft, not 3.28.
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Background
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
Many conversion factors are exact by definition. The inch has been defined as exactly 2.54 centimetres since 1959, and the pound as exactly 0.45359237 kilograms, so conversions involving them can be as precise as you need.
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
For any value, use the Watts to Horsepower Converter or browse all power converters.
Run your own numbers: Watts to Horsepower Converter