HP to Amps Calculator
Convert horsepower (HP) to current in amperes (A) using voltage, efficiency, and phase type. Ideal for motor sizing, electrical design, and generator planning.
Understanding Horsepower to Amps Conversion
Converting horsepower (HP) to current in amperes (A) is essential when designing or troubleshooting electrical systems. This is particularly important for electric motors, compressors, and pumps which are often rated in horsepower but consume electrical current measured in amps.
Conversion Formulas
Formulas depend on whether the power supply is single-phase or three-phase:
- Single-phase: A = (HP × 746) ÷ (V × Efficiency)
- Three-phase: A = (HP × 746) ÷ (√3 × V × Efficiency)
What is Horsepower (HP)?
Horsepower is a unit of mechanical power. In electrical systems, it’s used to rate motors. 1 horsepower is equal to 746 watts of power.
Why Efficiency Matters
Motors are not 100% efficient. The efficiency value accounts for energy loss due to heat, friction, and other factors. A typical motor has an efficiency between 0.85 and 0.95.
Example Conversions
- Single-phase, 5 HP, 240 V, 90% efficient: A = (5 × 746) ÷ (240 × 0.9) ≈ 17.27 A
- Three-phase, 10 HP, 400 V, 0.92 efficiency: A = (10 × 746) ÷ (1.732 × 400 × 0.92) ≈ 11.67 A
Applications
- Electric motor sizing
- Overcurrent protection design (breakers/fuses)
- Wiring and conductor selection
- Generator and UPS sizing
Motor Efficiency Reference Table
| Motor Size (HP) | Typical Efficiency | Usage Type |
|---|---|---|
| 1 HP | 0.85 – 0.90 | Small fan, pump |
| 5 HP | 0.89 – 0.91 | Air compressors |
| 10 HP | 0.91 – 0.93 | Industrial motors |
| 50 HP | 0.94 – 0.96 | HVAC, large pumps |
FAQs
Is HP a measure of electrical power?
No. HP measures mechanical power, but can be converted to watts or amps in electrical systems.
Do I need to include power factor?
No. Power factor is already considered in the conversion via efficiency, unless working with reactive loads.
Can this calculator be used for DC motors?
No. This calculator is designed for AC systems. DC systems have different conversion formulas.
How accurate is this calculation?
It's an approximation. Real-world conditions (startup current, load type) may vary slightly.