Horsepower to Watts
An instant horsepower-to-watts converter, with the formula and a reference table below.
| Horsepower | Watts |
|---|---|
| 1 hp | 745.699872 W |
| 2 hp | 1491.399743 W |
| 3 hp | 2237.099615 W |
| 5 hp | 3728.499358 W |
| 10 hp | 7456.998716 W |
| 25 hp | 18642.49679 W |
| 50 hp | 37284.993579 W |
| 100 hp | 74569.987158 W |
How to use
- Enter a value in the Horsepower field.
- The Watts figure appears immediately — no button to press.
- Typing in the Watts field converts back to Horsepower the same way.
- Use the reference table for the values that come up most often.
Horsepower to Watts formula
The factor from horsepower to watts is 745.699872.
W = hp × 745.699872
Why this factor: the horsepower and the watt are both defined against the watt, so dividing one definition by the other gives 745.699872 directly. Both definitions are set out in full below.
To go the other way, divide by 745.699872 — or use the Watts to Horsepower converter, which is the same calculation reversed.
Worked example
Given 500 hp, multiplying by 745.699872 yields 372849.935791 W.
500 hp × 745.699872 = 372849.935791 W
The converter above does this for any value you type, in either direction.
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.
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.
Horsepower vs Watts
The horsepower is an imperial unit while the watt is an SI 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 watts are in a horsepower?
One horsepower equals 745.699872 watts.
What is the formula to convert horsepower to watts?
Multiply the number of horsepower by 745.699872. To reverse it, divide by 745.699872 instead.
How do I convert watts back to horsepower?
Divide by 745.699872, which is the same as multiplying by 0.00134102209.
How many watts are in 10 horsepower?
10 hp works out to 7456.998716 W.
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 horsepower defined?
Defined as 550 foot-pounds per second, which is about 745.700 watts.