Formula variables
- hp is motor horsepower.
- V is the selected single-phase voltage.
- Efficiency is entered as a percent and converted to decimal form.
- PF is motor power factor.
Assumptions
- The estimate uses single-phase motor current arithmetic.
- Voltage, efficiency, and power factor should match the motor nameplate or manufacturer data when available.
- Single-phase motors can have high starting current that is not included in this full-load estimate.
- This calculator does not replace motor nameplate FLA, starting-current review, conductor sizing, overload selection, branch-circuit protection, or installation approval.
Examples
1 hp at 240 V. A 1 hp single-phase motor at 240 V, 72 percent efficiency, and 0.72 PF estimates about 6.0 A.
120 V sensitivity. The same horsepower at 120 V produces roughly twice the current of 240 V before nameplate review.