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HP to Amps Calculator and Amps to HP

Convert horsepower to amps, or amps to HP, for motors and pumps. The current a motor draws depends on its voltage, efficiency, and power factor, so set those and WattSimple estimates the amps plus the NEC wire and breaker the circuit calls for.

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%

Current draw

19.18 A

Horsepower
5 HP
Current at 240 V
19.18 A

NEC wire & breaker for this load

Breaker
20 A
Min. copper wire (75°C)
12 AWG

Copper, 75°C terminations, NEC Table 310.16. Real installs may need derating for ambient heat, conduit fill, or voltage drop. Full wire & breaker chart. Always confirm with a licensed electrician + local AHJ.

An estimate from efficiency and power factor. Real motor circuits are sized from the NEC 430 full-load-current tables on the nameplate: confirm with a licensed electrician.

Measure the real amps and volts

The converter works from nameplate or assumed figures. A clamp meter reads the actual current on one conductor without breaking the circuit; clamped around a whole cord it reads close to zero. A multimeter reads the voltage at the receptacle or terminals. Opening a panel or a live box is work for someone qualified.

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Frequently asked questions

First convert horsepower to the electrical watts the motor draws: output watts (HP × 746) divided by efficiency, then divide by the voltage (and by power factor, and √3 for three-phase) to get amps. For example, a 5 HP single-phase motor at 240 V, 90% efficiency, and 0.9 power factor draws roughly 19 amps.

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Sources & standards

This tool's methodology and data follow US standards and authoritative public datasets: