Calculate current draw for loads
This calculator determines the current draw (amperage) for electrical equipment based on power consumption and voltage.
Single Phase: I = W / (V × PF)
Three Phase: I = W / (√3 × V × PF)
Horsepower to Watts: 1 HP = 746 Watts
Common amp draws:
• 1500W space heater @ 120V = 12.5A
• 5HP motor @ 240V = 19.5A
• 10kW heater @ 240V = 41.7A
Power Factor: Motors have PF of 0.8-0.85. Heaters, lights, and resistive loads are 1.0. When in doubt, use 0.85 for motors.
How to use: Select voltage and phase, enter power in watts/HP/kW, set power factor. Calculator shows amp draw for proper circuit sizing.