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HP to kW Calculator

Convert horsepower to kilowatts, or kW to HP, for motors, pumps, generators, and EV drivetrains. Set the motor efficiency and voltage and WattSimple also estimates the current draw and the NEC wire and breaker it points to.

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%

Mechanical power

3.73 kW

Shaft output
5 HP · 3.73 kW
Electrical input
4,143 W
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.

HP ↔ kW is exact (1 HP = 745.7 W output); the amps and wire are an estimate from your 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.

Frequently asked questions

One mechanical (shaft) horsepower equals 745.7 watts, so kW = HP × 0.7457. For example, 5 HP = 3.73 kW. To go the other way, HP = kW ÷ 0.7457. This is the shaft output power; the electricity the motor draws is higher because no motor is 100% efficient.

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Sources & standards

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