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Power Converter

Convert power between watts and multiples, three kinds of horsepower, BTU per hour, foot-pounds per second, calories per second and tons of refrigeration. These are all rates of energy transfer: the page uses exact definitions such as 1 hp = 550 ft·lbf/s = 745.69987158227 W and 1 ton of refrigeration = 12 000 BTU/h.

Unit Converters Runs in your browser

Convert Power or Rate of Energy

Mechanical horsepower (745.7 W), metric horsepower or PS (735.49875 W) and electrical horsepower (746 W) are different units and are listed separately. Negative values are accepted.

Decimals and scientific notation such as 1.5e3 are accepted.
Automatic shows exact results in full and rounds long ones to 12 significant digits. A value too small for the chosen decimal places is shown with 3 significant digits instead of 0.

How to Use the Power

  1. Type the value you want to convert in Value to convert.
  2. Pick the starting power unit in From unit and the one you want in To unit. The lists are grouped by measurement system.
  3. Read the result and the formula directly under the form; it updates as you type. Use Swap units to reverse the direction.
  4. Scroll to the table to see the same value in every available unit, change Precision if you need fewer digits, or press Copy result.

About This Tool

Car and engine buyers comparing hp and kW, HVAC and air-conditioning installers sizing equipment, electricians and solar installers, appliance shoppers, and engineering students.

Input: A number and a unit  ·  Output: The same power in every unit.

Features and Limitations

Features

  • Exact: 1 hp = 550 ft·lbf/s, 1 PS = 75 kgf·m/s = 735.49875 W, 1 hp(E) = 746 W, 1 BTU(IT)/h = 0.29307 W.
  • Mechanical, metric and electrical horsepower kept apart and clearly labelled.
  • Ton of refrigeration (12 000 BTU/h) for cooling equipment.
  • Formula text, equivalence line and a table of the power in every unit.

Limitations

  • “Brake horsepower”, “shaft horsepower” and “indicated horsepower” describe where power is measured, not different units; convert them as ordinary horsepower.
  • Power is a rate. To convert energy amounts such as kWh or BTU use the Energy Converter.
  • Results are computed in your browser; nothing you enter is sent to a server.

Example

1 hp = 745.6999 W = 0.7457 kW. 100 hp = 74.57 kW. 150 kW = 201.153 hp. 1 PS = 735.49875 W, so 1 hp = 1.01387 PS. 1 kW = 3412.14 BTU/h. 1 ton of refrigeration = 3.51685 kW = 12 000 BTU/h.

Frequently Asked Questions

How many watts are in a horsepower?

Mechanical (imperial) horsepower is 745.69987158227022 W, from 550 foot-pounds force per second. The rounded figure 746 W is the electrical horsepower used for motors; metric horsepower is 735.49875 W.

Is metric horsepower the same as horsepower?

No. A metric horsepower (PS, CV, pk) is 75 kgf·m/s = 735.49875 W, about 1.4 % smaller than a mechanical horsepower. European car brochures use PS or kW, American ones hp, so a 150 PS engine is about 148 hp.

What is a ton of refrigeration?

A unit of cooling capacity equal to 12 000 BTU per hour (3.517 kW). It comes from the heat needed to melt one short ton of ice in 24 hours. It is not a weight.

What is the difference between kW and kWh?

A kilowatt is a rate of energy use (power); a kilowatt-hour is the energy used by running at one kilowatt for one hour. A 2 kW heater running for 3 hours uses 6 kWh.

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