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Power Unit Conversion Reference

Convert watt, kilowatt, horsepower, and BTU/h instantly.

Convert between watts, kilowatts, megawatts, metric and mechanical horsepower, BTU per hour, kcal/h, and ft-lb/s using exact SI factors, all in your browser.

What is the base unit used?

The watt (W), the SI unit of power equal to one joule per second. Every input is converted to watts first, then out to every other unit, so chained rounding cannot accumulate.

One place for every power unit

Power is the rate of energy transfer. Engineers use watts and kilowatts, car makers quote horsepower (in two different definitions), and HVAC equipment is rated in BTU per hour. This reference converts between all of them from a single input.

How it works

Each unit has an exact factor to the SI base, the watt. Your value is converted to watts first, then out to each target unit:

1 kW   = 1000      W
1 MW   = 1000000   W
1 hp   = 745.6999  W   (mechanical / imperial)
1 PS   = 735.49875 W   (metric horsepower)
1 BTU/h= 0.293071  W
1 kcal/h = 1.163   W
1 ft-lb/s = 1.355818 W

Because everything routes through one base unit, no error builds up the way it does when you multiply a chain of unit-to-unit factors.

Tips and notes

  • Always confirm which horsepower a spec uses: PS (735.5 W) and hp (745.7 W) are not equal.
  • A rough rule: 1 kW is about 1.34 mechanical hp or 1.36 metric PS.
  • HVAC: 12,000 BTU/h equals one ton of cooling, roughly 3.5 kW.
  • Electrical heaters labelled in kW deliver that power as heat directly (1 kW = 1 kW of heat).