How many watts are in a horsepower?

One mechanical horsepower is about 745.7 watts. Metric horsepower, sometimes written PS, is slightly less at about 735.5 watts.

A kilowatt is 1000 watts. Car engines and heaters are often rated in kilowatts in New Zealand, while older figures may use horsepower.

What is BTU per hour?

BTU per hour is a power unit common in heating and air conditioning. One watt is about 3.412 BTU per hour, so a heat pump's BTU rating can be converted to kilowatts.

Power Converter

This power converter switches a figure between the units used to measure power, the rate at which energy is used or produced. Power turns up in many guises depending on the field: electrical and heating equipment is rated in watts and kilowatts, engines are quoted in horsepower, and heating and air conditioning systems often use BTU per hour, so being able to move between them is genuinely useful. You enter a value, choose the unit it is in and the unit you want, and the converter returns the result instantly. The conversions use the standard definitions, where a kilowatt is 1000 watts, one mechanical horsepower is about 745.7 watts, metric horsepower or PS is about 735.5 watts, and one watt is about 3.412 BTU per hour. This makes it easy to compare a car engine quoted in horsepower against one in kilowatts, to size a heat pump where the BTU rating needs to become kilowatts, or to read an imported appliance's specifications. In New Zealand, engine power and heating output are usually given in kilowatts, so converting older or overseas horsepower and BTU figures helps you compare like with like. Enter a value and pick your units to see the converted power straight away.

How it works

Each unit has a known size in watts, the SI base unit of power. The converter changes your value into watts, then into the target unit, so any pair of units can be converted in one step.

Worked example

A 100 kilowatt engine is 100 times 1000, which is 100,000 watts, and dividing by 745.7 gives about 134 mechanical horsepower.

Related calculators

Energy Converter: joules, kWh, calories.
Electrical Power Calculator: P equals V I.
Pressure Converter: kPa, bar, psi.
Watts to Amps Calculator: current from power.

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