Calcylator
Mechanical Horsepower to Watts

Horsepower to watts:
multiply by 745.7

Convert mechanical horsepower to watts for motors, pumps and appliances, with a chart, worked examples and the horsepower definitions to watch.

Calcylator Editorial Team

Updated · 5 min read

How many watts are in a horsepower?

One mechanical horsepower is 745.6998716 watts, about 745.7 W. That is also 0.7457 kilowatts, so four horsepower is a little under three kilowatts.

The unit was created to describe how much work an engine could do compared with a horse, and the modern value is fixed by definition. Because the watt is the SI unit of power, converting hp to watts is the usual step before comparing a motor with an electrical supply.

The hp to watts formula

Mechanical horsepower to watts =W = hp × 745.6998716
W:
power in watts
hp:
power in mechanical horsepower
745.6998716:
watts in one mechanical horsepower
To go the other way, multiply watts by 0.00134102209 to get hp.

  • Power

    3 hp

  • Multiply

    3 × 745.6998716

Power in watts

2,237.1 W

The full result is 2237.0996148 W, or 2.24 kW.

For a mental estimate use 750 W per hp. Three hp becomes 2,250 W by that shortcut, within about 0.6 percent.

  1. Read the motor rating in hp from the plate.
  2. Multiply by 745.6998716 for watts.
  3. Divide by 1,000 if you want kilowatts.
  4. Check with hp × 750, which should be very slightly higher.

Chart: horsepower to watts from 1 to 1000

The values are exact, so you can pick the row that matches your motor.

Mechanical horsepower to watts
HorsepowerWatts
1745.6998716
21491.399743
53728.499358
107456.998716
2518642.49679
5037284.99358
10074569.98716
250186424.9679
500372849.9358
1000745699.8716

Five hp is about 3.7 kW and 10 hp is about 7.5 kW, sizes often seen in workshop compressors and small pumps.

Where hp to watts is used

A garden pond pump rated at 0.25 hp draws about 0.25 × 745.6998716 = 186.4 W of mechanical output. The electrical input is higher because motors lose some energy as heat, so check the plate for the actual consumption.

Going the other way, a 1,500 W kitchen heater is 1500 × 0.00134102209 = 2.01 hp. Shop vacuums, saws and mixers are often advertised in horsepower, and this lets you compare them with a watt rating on the box.

Likewise, an 8 hp engine delivers about 5.97 kW at the shaft. A generator driven by it will supply less electrical power than that, so allow for losses when counting appliances.

Common mistakes converting hp to watts

  • Mixing horsepower definitions. Mechanical hp is 745.7 W, electrical hp is 746 W and metric hp is 735.5 W, so check which one a label means.
  • Confusing output with input. A motor's rated hp is usually shaft output, and the electricity it draws is higher.
  • Dividing when you should multiply. Watts are small, so one hp gives a number in the hundreds.
  • Treating peak and continuous ratings alike. A tool marketed as 5 hp peak may deliver far less continuously.

Common questions

How many watts is 1 horsepower?

One mechanical horsepower is 745.6998716 watts, about 745.7 W or 0.7457 kW. To convert, multiply the horsepower by 745.6998716. A 10 hp motor is therefore about 7,457 watts, or 7.46 kilowatts.

How do I convert hp to watts?

Multiply the horsepower by 745.6998716. For example, 3 hp is 3 × 745.6998716 = 2,237.1 W. A quick check is to multiply by 750, which gives 2,250 W and lands very close.

How many hp is 1500 watts?

1,500 watts is about 2.01 mechanical horsepower, found by multiplying 1,500 by 0.00134102209. That is a typical rating for a room heater, so it is a little over 2 hp.

Is 1 hp equal to 746 watts?

Almost. Electrical horsepower is defined as 746 W, while mechanical horsepower, used by this converter, is 745.7 W. The difference is 0.04 percent, so it rarely matters for everyday use.

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