kW to HP Calculator

How it works

Horsepower is a unit of power, like the watt, so converting is a single multiplication. The calculator turns your value into watts, then divides by the number of watts in the horsepower you chose.

There are three common horsepowers. Mechanical horsepower is 550 foot-pounds per second, 745.69987 W. Electrical horsepower is defined as exactly 746 W. Metric horsepower (PS, CV or ch) is 75 kilogram-force metres per second, exactly 735.49875 W. The three differ by up to about 1.4%.

This is a unit conversion. A motor's horsepower rating is its mechanical output at the shaft; the electrical power it draws is larger by its efficiency losses.

Formula

watts = value × (watts per unit)
hp    = watts ÷ (watts per hp)

mechanical hp = 550 × 4.4482216152605 × 0.3048 = 745.69987 W
electrical hp = 746 W
metric hp (PS) = 735.49875 W
1 kW = 1.341022 hp (mechanical) = 1.340483 hp (electrical) = 1.359622 PS

Example

1 kW, the default, is 1,000 ÷ 745.69987 = 1.341022 mechanical horsepower. The table shows the same kilowatt as 1.340483 electrical hp and 1.359622 metric hp.

A 20 hp motor rating in electrical horsepower is 20 × 746 = 14,920 W, or 14.92 kW. In mechanical horsepower it is 20 × 745.69987 = 14,913.997 W.

Assumptions and limitations

• This is a unit conversion only. A motor's nameplate horsepower is shaft output; the electrical input in kW is the output divided by the motor's efficiency, so the power drawn from the supply is higher than the converted figure.
• Mechanical hp uses the exact pound-force and foot (745.69987158 W). Electrical hp is exactly 746 W and metric hp exactly 735.49875 W, the values listed in NIST Special Publication 811 (2008 edition), Appendix B.9.
• Boiler horsepower (about 9,809.5 W) and other specialised horsepowers are different units and are not offered.
• Results are rounded for display; the conversion is computed in full precision.

Frequently asked questions