Horsepower to Amps Calculator

Enter horsepower, volts, and motor efficiency below to convert to amps.

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How to Convert Horsepower to Amps

Horsepower (HP) is a measure of electric power equal to 746 watts (W). Converting horsepower to amps can be done in a few simple steps, or using this simple formula.

Amps = (Horsepower × 746) ÷ Efficiency ÷ Volts

Continue reading to see how this formula was derived.

Convert Horsepower to Watts

The first step to convert HP to amps is convert HP to watts. Since 1 HP is equal to 746 W simply multiply the horsepower by 746 for this conversion.

Watts = Horsepower × 746

Account for Efficiency

Since motors are not 100% efficient, the number of amps needed to achieve the power output is actually higher depending on the efficiency. To find this, divide the horsepower by the efficiency η in decimal form.

Watts = Watts η

Convert to Amps

After the power has been converted to watts, use the Watt's Law formula to find current in amps.

Amps = Watts ÷ Volts

After the steps above the final formula for converting horsepower to amps is:

Amps = HP × 746 V × η × PF

Thus, the current in amps is equal to horsepower times 746 divided by the voltage times the efficiency η times the power factor.

formula to convert horsepower to amps

For example, let's find the current draw in amps of a 1 horsepower motor that runs at 120 volts with a 90% efficiency.

Amps = 1 HP × 746 W 120 V × .9
Amps = 746 120 V × .9
Amps = 746 108
Amps = 6.9 A

Common Horsepower to Amps Conversions

Current measurements in amps for common horsepower values at 120 volts for a motor with 90% efficiency.
Horsepower Amps Voltage Efficiency
.25 HP 1.73 A 120 V 90%
.5 HP 3.45 A 120 V 90%
.75 HP 5.18 A 120 V 90%
1 HP 6.91 A 120 V 90%
1.25 HP 8.63 A 120 V 90%
1.5 HP 10.4 A 120 V 90%
1.75 HP 12.1 A 120 V 90%
2 HP 13.8 A 120 V 90%
2.5 HP 17.3 A 120 V 90%
3 HP 20.7 A 120 V 90%
3.5 HP 24.2 A 120 V 90%
4 HP 27.6 A 120 V 90%
4.5 HP 31.1 A 120 V 90%
5 HP 34.5 A 120 V 90%
10 HP 69.1 A 120 V 90%

Also be sure to check out our amps to horsepower calculator.