Watt Horsepower Converter
Convert watts, kilowatts, mechanical horsepower, metric horsepower, and electric horsepower on one screen. Enter a value, choose the horsepower standard, and the result window and summary cards update immediately.
Input
Result
ready to use.
- Visible firstKeep the input and result positions clear.
- Results firstPut the main number up front and keep the process secondary.
- Less to askNo sign-up or extra information before using the tool.
Read watts and horsepower from the same power basis
The watt horsepower converter rewrites one power value as W, kW, HP, PS, and electric HP. Watts are the SI power unit used in electrical products, motor ratings, and technical documents. Horsepower is still common in engine, pump, and motor descriptions because it is easier to compare at a glance.
Use the left input window for the known value, then choose the horsepower standard. Mechanical horsepower, metric horsepower, and electric horsepower do not use the same watt value, so a document marked HP, PS, or HP(E) should be matched before you compare the numbers.
Use it in screen order
- If you know watts or kilowatts, keep the input in W and enter the number. A value such as 1000 W is converted to the selected horsepower standard on the right.
- If you know horsepower, use the direction switch to enter HP. The tool converts that horsepower value back to W and kW.
- The horsepower selector is the calculation basis. Match HP, PS, or HP(E) to the source document before copying the result.
- The summary cards show the same power as kW, mechanical HP, metric PS, and electric HP(E) together.
Units and basis
- W is watt, the SI unit of power. 1 kW equals 1000 W.
- Mechanical horsepower HP is based on 550 ft·lbf/s. The NIST conversion table lists 1 HP as about 745.6999 W; this tool uses 745.699872 W for calculation.
- Metric horsepower PS is common in European and Asian vehicle data. This page uses 1 PS = 735.4988 W.
- Electric horsepower HP(E) is used in electric motor contexts and is treated as 1 HP(E) = 746 W.
Example conversions
The differences look small, but they matter when ratings are compared in a table or copied into a specification.
Rounding and cautions
- A source that only says HP may mean mechanical horsepower or metric horsepower depending on country and field. Check whether the original text says PS, metric horsepower, or electric horsepower.
- Electrical input power and motor output power can both be written in watts, but they do not always describe the same thing. Efficiency, power factor, and operating conditions need separate specifications.
- For quotes or technical notes, keep the original W or kW value, the horsepower standard, and the decimal precision instead of saving only a rounded horsepower number.
- This page is for unit conversion. Equipment selection and safety margin decisions should use the manufacturer rating table and site conditions.
FAQ
How many watts are in one horsepower?
Mechanical horsepower is 1 HP = 745.699872 W, metric horsepower is 1 PS = 735.4988 W, and electric horsepower is 1 HP(E) = 746 W. If a document does not say which horsepower it uses, the converted number can differ slightly.
Which horsepower type should I choose when converting watts?
Use mechanical horsepower for many U.S.-style HP engine references, metric horsepower when the source says PS or metric horsepower, and electric horsepower when an electric motor document uses HP(E).
Are kilowatts and horsepower both power units?
Yes. They both describe power, or work per unit time. Watts and kilowatts are SI units, while horsepower is a familiar auxiliary unit in vehicles and motor descriptions.
Why do horsepower standards give different values?
Mechanical, metric, and electric horsepower were defined in different historical and technical contexts. The gap is small, but the chosen basis should be recorded in ratings, comparisons, and quotes.
How many decimal places should I keep?
For everyday comparison, one or two decimal places is often enough. For product specs, quotes, and engineering notes, keep the original value, unit, selected horsepower standard, and rounding precision together.
References used
The watt and horsepower relationship here follows the horsepower conversion factors in the NIST power conversion table and the SI power unit system.