hp to amps Calculator

Created by Kenneth Alambra
Last updated: Aug 01, 2022

If you need to determine the amperage required to run an electrical system like a motor to provide a specified power, this hp to amps calculator is for you. Keep on reading to start learning:

  • The relationship between horsepower to amps;
  • How to convert horsepower to amps; and
  • How to use this hp to amps calculator.

What is the relationship between horsepower to amps?

Horsepower, abbreviated as hp, is a unit of power. While amperes or amps is a unit of electric current. We use both these units to describe the intensity of the electricity flowing from a power source. Imagine we need to run a 7-hp motor using a 220-volt alternating current (AC) power source. We can use Ohm's Law to determine how much amperage we need to run this motor. Let's find how in the next section of this text.

How to convert hp to amps

To find the required current to run a 7-hp motor with a 220 V voltage source, we can use this formula derived from Ohm's Law:

I=746×PV×PF×η×cI = \frac{746\times P}{V\times PF\times \eta\times c}

where:

  • II is the required current in amps;
  • PP is the power in electrical horsepower;
  • VV is the voltage in volts;
  • PFPF is the power factor for three-phase systems with values from 0 to 1;
  • η\eta is the system's efficiency; and
  • cc is a multiplier with values equal to 11 for DC or single-phase AC, 3\sqrt3 for three-phase AC (line-to-line voltage), or 33 for three-phase AC (line-to-neutral voltage).

💡 In our hp to amps conversion formula, we have 746 there as a conversion factor from horsepower to watts. So, if you want to convert watts to amps, simply remove 746 from the equation to get the correct results. On the other hand, use 745.7 if you're converting from mechanical horsepower to amps.

Let's say our 7-hp motor has a power factor of 0.8 and an efficiency of 90% (or 0.9). We now convert our motor hp to amps by substituting our known parameters to the formula, as shown below:

I=746×PV×PF×η×c=746×7 hp220 volts×0.8×0.9×1=5222 watts158.4 volts=32.97 amperes\small \begin{align*} I &= \frac{746\times P}{V\times PF\times \eta\times c}\\\\ &= \frac{746\times 7\ \text{hp}}{220\ \text{volts}\times 0.8\times 0.9\times 1}\\\\ &= \frac{5222\ \text{watts}}{158.4\ \text{volts}}\\\\ &= 32.97\ \text{amperes}\\\\ \end{align*}

How to use this hp to amps calculator

With our hp to amps calculator, you don't have to worry about memorizing the formula to convert horsepower to amps. All you have to do is follow these steps, and you're good to go.

  1. Select your electric current type, whether it's DC, AC single-phase, or AC three-phase.
  2. Enter the target power you need to meet. Our tool has the unit for this in electrical hp, hp(E), but you can change this to other units like mechanical hp or watts.
  3. Input the voltage your electrical system will need to run.
  4. Type in the efficiency and power factor (if your electrical system runs on AC).

After performing these steps, you will see that our tool instantly converts hp to amps for you. 🙂

Kenneth Alambra
Current type
DC
Power (hp)
hp(E)
Voltage (V)
V
Efficiency (η)
%
Amperage (amps)
A
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