Power Unit Converter

Type a value in any row: the other eight update as you go, and Convert repeats the run from the row you started in. Metric horsepower (PS) and mechanical horsepower (hp) are different units, and 1 kcal/s is 4186.8 W.

Runs locally in your browser

How to convert between power units

This converter turns one power value into nine units at once: metric horsepower (PS), kilocalories per second, kilowatts, mechanical horsepower (hp), foot-pounds per second, watts, BTU per second, kilogram-force metres per second and newton metres per second. The factors are the definitions rather than rounded decimals: 1 PS = 75 kgf·m/s = 735.49875 W, 1 hp = 550 ft·lbf/s = 745.6998715822702 W, 1 kcal/s = 4186.8 W (the IT calorie, 1 cal = 4.1868 J) and 1 BTU/s = 1055.05585262 W.

Type a number into the row whose unit you have: the other eight rows follow every keystroke, and Convert on that row repeats the run and reports it in the status line. Everything is calculated in the browser, so no value is sent anywhere.

  1. Find the row with the unit you already know and type the value there.
  2. Read the other eight rows; they update while you type.
  3. Press Convert on the row you typed in to re-run the conversion and see the confirmation line.
  4. Press Reset all to empty the table and start over.
  5. Results carry twelve significant digits; watts, joules per second and newton metres per second always agree because they are the same unit.

What the numbers mean

The nine units and their definitions

1 PS (metric horsepower) is 75 kgf·m/s = 735.49875 W. 1 hp (mechanical horsepower) is 550 ft·lbf/s = 745.6998715822702 W. 1 kcal/s is 4186.8 W with the IT calorie (1 cal = 4.1868 J). 1 BTU/s is 1055.05585262 W with the IT BTU. 1 ft·lbf/s is 1.3558179483314004 W (0.3048 m × 0.45359237 kg × 9.80665 m/s²). 1 kgf·m/s is 9.80665 W, 1 kW is 1000 W, and 1 W is 1 J/s and 1 N·m/s.

The metric and mechanical horsepower are two different units: 1 PS = 0.98632007062 hp and 1 hp = 1.01386966542 PS, about 1.4 % apart. The joule-per-second, watt and newton-metre-per-second rows are kept because the page has always shown them, but their figures are identical by definition.

Worked examples

1 PS = 0.73549875 kW = 75 kgf·m/s = 735.49875 W. 1 kW = 1.3596216173 PS = 1.3410220896 hp = 0.238845896627 kcal/s. 1 hp = 550 ft·lbf/s = 1.01386966542 PS.

100 hp = 74.5699871582 kW. 3.5 kW = 4.75867566056 PS. 75 kgf·m/s = 735.49875 W. These are the figures the page prints for those inputs.

Input rules and limits

Digits with one decimal point are expected; a comma is answered with a hint instead of being deleted, and exponent notation such as 1e3 is accepted. A leading minus sign is kept, because a negative power is a direction. Results are rounded to twelve significant digits, and a value that overflows the browser number range is refused with a message.

The page converts power only: it does not apply a power factor or a three-phase correction, it has no BTU/h or refrigeration-ton row, and no unit can be added. Nothing is uploaded and no request is made.

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