Amps to Horsepower Calculator
Enter amps, volts, and motor efficiency to calculate the horsepower.
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How to Convert Amps to Horsepower
The conversion from amps, a measure of electric current, to horsepower, a measure of power output by a motor, can be done using a fairly simple formula.
Horsepower = I(A) × V(V) × η × PF / 746
Thus, horsepower is equal to the current in amps times the voltage in volts times the efficiency times the power factor, divided by 746.
How did we get that? Since horsepower is a measure of electric power, Watt’s Law can be used to convert. Watt’s Law gives us the formula to solve power given voltage and current using this formula.
Watts = Amps × Volts
After converting amps and volts to watts, the next step is to convert watts to horsepower.
| Horsepower | Watts |
|---|---|
| 1 Electric HP | 746 watts |
| 1 Mechanical HP | 745.7 watts |
Because 1 horsepower is equal to 746 watts, the formula above will include a division by 746 to complete the conversion.
One additional consideration that should be made when doing the conversion is the efficiency of the motor being used. Motors are often only 80% to 90% efficient, which means that they can only produce 80% to 90% of energy output for the amount of power in.
When converting to horsepower the efficiency can be accounted for by multiplying the result by the efficiency in decimal form.
For example, let’s find the horsepower of a motor drawing 8 amps at 120 volts that is 90% efficient.
HP = I(A) × V(V) × η × PF) / 746
HP = 8 A × 120 V × .9) / 746
HP = 864 / 746
HP = 1.158 HP
Common Amps to Horsepower Conversions
| Amps | Horsepower | Voltage | Efficiency |
|---|---|---|---|
| 1 A | .14 HP | 120 V | 90% |
| 2 A | .29 HP | 120 V | 90% |
| 3 A | .43 HP | 120 V | 90% |
| 4 A | .58 HP | 120 V | 90% |
| 5 A | .72 HP | 120 V | 90% |
| 6 A | .87 HP | 120 V | 90% |
| 7 A | 1.01 HP | 120 V | 90% |
| 8 A | 1.16 HP | 120 V | 90% |
| 9 A | 1.3 HP | 120 V | 90% |
| 10 A | 1.45 HP | 120 V | 90% |
| 15 A | 2.17 HP | 120 V | 90% |
| 20 A | 2.9 HP | 120 V | 90% |
| 25 A | 3.62 HP | 120 V | 90% |
| 30 A | 4.34 HP | 120 V | 90% |
We also have a horsepower to amps calculator that you may find useful.