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Generator Size Calculator

HP to Amps Calculator

Accurately convert motor Horsepower (HP) to electrical current (Amps). Includes full support for DC, Single-Phase, and Three-Phase systems.

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Motor Specs

HP
%

Result

Estimated Current

-- Amps

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HP to Amps Formulas

To manually calculate the electrical current drawn by a motor, use the formulas below. The conversion relies on the constant 1 HP = 746 Watts.

DC Motor

Amps = (HP × 746) / (V × Efficiency)

Single-Phase AC

Amps = (HP × 746) / (V × Efficiency × PF)

Three-Phase AC

Amps = (HP × 746) / (V × 1.732 × Efficiency × PF)
  • V (Voltage): Line-to-line voltage for 3-phase, line-to-neutral for 1-phase.
  • Efficiency: Motor efficiency expressed as a decimal (e.g., 90% = 0.90).
  • PF (Power Factor): Applicable only to AC circuits (e.g., 0.85).
  • 1.732: The square root of 3 (√3), used in three-phase power calculations.

HP to Amps Conversion Chart

Estimated full-load currents based on typical 90% efficiency and 0.85 power factor.

Motor HP 120V (1-Phase) 240V (1-Phase) 240V (3-Phase) 480V (3-Phase)
1/2 HP 4.1 A 2.0 A 1.2 A 0.6 A
1 HP 8.1 A 4.1 A 2.3 A 1.2 A
2 HP 16.3 A 8.1 A 4.7 A 2.3 A
5 HP 40.6 A 20.3 A 11.7 A 5.9 A
10 HP 81.3 A 40.6 A 23.5 A 11.7 A
20 HP N/A 81.3 A 46.9 A 23.5 A
50 HP N/A N/A 117.3 A 58.7 A
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