Motor HP to Amps Calculator
Estimate running motor current from shaft power and efficiency.
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What this tool does
Estimate running motor current from shaft power and efficiency. Starting current can be far higher; use nameplate and code motor tables for protection sizing.
How to use the Motor HP to Amps Calculator
- Enter or select mechanical horsepower.
- Enter or select voltage.
- Enter or select supply.
- Enter or select power factor.
- Enter or select motor efficiency (%).
- Read the calculated result; change any measurement to compare alternatives.
Formula
amps=HP×745.699872/(phase factor×voltage×PF×efficiency/100)
- hp
- Mechanical horsepower
- voltage
- Voltage
- phase
- Supply
- pf
- Power factor
- efficiency
- Motor efficiency (%)
Starting current can be far higher; use nameplate and code motor tables for protection sizing.
Worked example
For motor hp to amps calculator, the following measurements illustrate the exact method: Mechanical horsepower: 5; Voltage: 240; Supply: 1; Power factor: 0.9; Motor efficiency (%): 90.
Inputs
- Mechanical horsepower5
- Voltage240
- SupplySingle phase
- Power factor0.9
- Motor efficiency (%)90
Result
- Estimated current (amps)19.18
Results explained
- Estimated current (amps)
- Estimated current (amps) from the formula above. Starting current can be far higher; use nameplate and code motor tables for protection sizing.
Frequently asked questions
amps=HP×745.699872/(phase factor×voltage×PF×efficiency/100)
Starting current can be far higher; use nameplate and code motor tables for protection sizing.
No. Electrical and HVAC results are estimates. Installation must comply with local codes and be checked by a qualified licensed professional.
Nameplate values, conductor temperature, power factor, efficiency, weather and actual installation conditions may differ from your entered assumptions.
Confirm units, manufacturer data and the formula's assumptions, then verify sizing with the equipment instructions and applicable local standards.