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Calculator Answers

Horsepower to Amps Calculator

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

A horsepower to amps calculator computes the electrical current requirements of a mechanical motor based on its rated horsepower (HP). Since mechanical work must account for internal thermal and magnetic losses, the tool converts horsepower to electrical watts (using the constant 746 watts per HP) and adjusts for the motor's efficiency and power factor. Electrical designers use it to size motor starters, contactors, and branch circuit protection.

Convert motor horsepower (HP) to current in amperes. Supports DC, single-phase AC, and three-phase AC electric motor calculations.

See also: Kilowatts to Amps Calculator, Watts to Amps Calculator, and Amps to Watts Calculator.

Quick Answer

Convert motor mechanical horsepower to current in amperes. Input horsepower, voltage, efficiency, and power factor to find amps.

Current Type

Value between 0 and 1 representing the conversion efficiency.

Formula Used

Amps = (HP × 746) / (Efficiency × Volts) = (1 × 746) / (0.85 × 120)

Horsepower to Amps

Current (Amperage)

7.3137 A

1 HP Motor at 120V

Horsepower1 HP
Mechanical Power746 W
Voltage120 V
Efficiency85%
Current7.3137 A

This calculator converts motor power in mechanical horsepower to electric current in amperes. It assumes 1 HP = 746 Watts of electrical power and factors in motor efficiency.

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How it works

Electric Motor Conversion Formulas

To convert mechanical horsepower (HP) to current in amperes (A), use these electrical formulas:

Direct Current (DC)

Amps = (HP × 746) / (Efficiency × Volts)

Alternating Current (AC) Single-Phase

Amps = (HP × 746) / (Efficiency × Power Factor × Volts)

Alternating Current (AC) Three-Phase

Amps = (HP × 746) / (1.732 × Efficiency × Power Factor × Volts)

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Frequently asked questions

First, convert horsepower to electrical watts (1 HP = 746 W). Then, divide the power in watts by the voltage and the motor's efficiency. For DC: A = (HP × 746) / (efficiency × V). For AC, also include the power factor: A = (HP × 746) / (efficiency × PF × V).

One mechanical horsepower is defined as exactly 746 watts of electrical power. In some electrical codes or contexts, a rounding of 746W is standard.

Small fraction-horsepower motors may have an efficiency of 50% to 70% (0.50 to 0.70). Larger industrial motors can achieve efficiencies of 85% to 95% (0.85 to 0.95).

For three-phase AC motors, the formula is: Amps = (HP × 746) / (1.732 × efficiency × Power Factor × Volts), where Volts is the line-to-line RMS voltage.