Watts to Horsepower
Type a value in either box to convert between watts and horsepower. The factor is 0.00134102.
| Watts | Horsepower |
|---|---|
| 1 W | 0.001341 hp |
| 2 W | 0.002682 hp |
| 3 W | 0.004023 hp |
| 5 W | 0.006705 hp |
| 10 W | 0.01341 hp |
| 25 W | 0.033526 hp |
| 50 W | 0.067051 hp |
| 100 W | 0.134102 hp |
How to use
- Enter a value in the Watts field.
- The Horsepower figure appears immediately — no button to press.
- Typing in the Horsepower field converts back to Watts the same way.
- Use the reference table for the values that come up most often.
Watts to Horsepower formula
Converting watts to horsepower is a single multiplication by 0.00134102209.
hp = W × 0.00134102209
Why this factor: the watt and the horsepower are both defined against the watt, so dividing one definition by the other gives 0.00134102209 directly. Both definitions are set out in full below.
To go the other way, divide by 0.00134102209 — or use the Horsepower to Watts converter, which is the same calculation reversed.
Worked example
Given 500 W, multiplying by 0.00134102209 yields 0.670511 hp.
500 W × 0.00134102209 = 0.670511 hp
The converter above does this for any value you type, in either direction.
What is a watt?
The watt is the SI unit of power — the rate of one joule of energy per second.
Definition: Defined as 1 J/s. Named after James Watt.
Where it is used: Appliance and light-bulb ratings, audio output, and all scientific power calculations.
What is a horsepower?
Mechanical horsepower is the traditional English-speaking unit of engine power.
Definition: Defined as 550 foot-pounds per second, which is about 745.700 watts.
Where it is used: US and UK car, motorcycle and small-engine power ratings.
Worth knowing: Distinct from metric horsepower (PS), which is about 1.4% smaller — so the same engine scores slightly higher in PS than in hp.
Watts vs Horsepower
The watt is an SI unit while the horsepower is an imperial unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many horsepower are in a watt?
One watt equals 0.00134102209 horsepower.
What is the formula to convert watts to horsepower?
Multiply the number of watts by 0.00134102209. To reverse it, divide by 0.00134102209 instead.
How do I convert horsepower back to watts?
Divide by 0.00134102209, which is the same as multiplying by 745.699872.
How many horsepower are in 10 watts?
10 W works out to 0.01341 hp.
Is there anything to watch out for with horsepower?
Distinct from metric horsepower (PS), which is about 1.4% smaller — so the same engine scores slightly higher in PS than in hp.
How is the watt defined?
Defined as 1 J/s. Named after James Watt.