ConverterHub

Power Converter

Convert between power units.

How it is calculated

The value is first converted to watts using the factor of the unit you pick, and the watt figure is then shown in watts, kilowatts and mechanical horsepower. Factors to watts: 1 W = 1, 1 kW = 1,000, 1 hp (mechanical, also called imperial) = 745.6998715823 W and 1 PS (metric horsepower) = 735.49875 W. So kW = W ÷ 1000 and hp = W ÷ 745.6998715823. The three results are rounded to two decimals. The output horsepower is the mechanical one, so a PS value comes out slightly lower in hp, and car makers' PS and hp ratings are not interchangeable.

Worked example

Convert 150 hp (mechanical horsepower) to other units. Watts: 150 × 745.6998715823 = 111,854.98 W. Kilowatts: 111,854.98 ÷ 1,000 = 111.85 kW. Back in horsepower: 111,854.98 ÷ 745.6998715823 = 150.00 hp. If the same 150 had been entered as PS, the watt value would be 150 × 735.49875 = 110,324.81 W.

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Common mistakes

  • Treating PS (metric horsepower) and hp (mechanical) as identical. They differ by about 1.4%, enough to matter on a spec sheet.
  • Dividing by 1,000 twice when going from W to kW, or expecting the answer to be in MW.
  • Reading a brake horsepower rating of an engine as the power at the wheels, which is lower after drivetrain losses.
  • Mixing power (kW) with energy (kWh). This tool only converts power.

About this calculator

This converter switches power values between watts, kilowatts, and horsepower, using the standard mechanical conversion of 1 horsepower = 745.7 watts (the mechanical horsepower; metric horsepower, PS, is offered separately at 735.5 watts). Watts and kilowatts convert by a simple factor of 1,000.

It's used when comparing a car or motor's horsepower rating to the kilowatt figures used on European spec sheets, when sizing a generator or solar inverter listed in watts against an appliance's horsepower draw, or when an engineer needs to cross-check a manufacturer's datasheet that mixes unit systems.

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