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.
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
| 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.