HP to Amps Calculator
Convert horsepower to amperage for electric motors and devices
Calculate Power and Current Conversion
Motor or device power rating
Operating voltage
Motor efficiency (typically 80-98%)
Conversion Results
Formula Used: I = P × 746 / (V × η)
Calculation: 0.0 W ÷ (0.0 V × 0.95 η)
Applications: Motor sizing, electrical load analysis, circuit design
Physical Interpretation
Example Calculation
1 HP Motor Current Draw
Power: 1 hp(E) = 746 W
Voltage: 200 V (single-phase AC)
Efficiency: 90%
Power Factor: 0.92
Calculation
I = P × 746 / (V × PF × η)
I = 1 × 746 / (200 × 0.92 × 0.9)
I = 746 / 165.6
I = 4.505 A
Common Motor Ratings
Key Concepts
Higher voltage = lower current for same power
Efficiency affects actual power consumption
Power factor important for AC motors
1 hp(E) = 746 watts exactly
Understanding HP to Amps Conversion
What is Horsepower?
Horsepower (hp) is a unit of power that measures the rate of energy transfer. Originally defined by James Watt, one horsepower equals the power needed to move 550 pounds one foot in one second, or equivalently 33,000 foot-pounds per minute.
Types of Horsepower
- •Electrical HP: 746 watts exactly
- •Mechanical HP: 745.7 watts
- •Boiler HP: 9,809.5 watts
Conversion Formulas
DC: I = P × 746 / (V × η)
AC Single-phase: I = P × 746 / (V × PF × η)
AC 3-phase L-L: I = P × 746 / (√3 × V × PF × η)
- I: Current (amperes)
- P: Power (horsepower)
- V: Voltage (volts)
- η: Efficiency (decimal)
- PF: Power factor (0-1)
- 746: Conversion factor (W/hp)
Applications and Examples
Practical Applications
- • Electric motor current sizing
- • Circuit breaker selection
- • Wire gauge determination
- • Load analysis for electrical panels
- • Energy consumption calculations
- • Motor starter sizing
Motor Efficiency Guidelines
- • Small motors (< 1 HP): 70-85%
- • Medium motors (1-10 HP): 85-92%
- • Large motors (> 10 HP): 92-98%
- • Premium efficiency motors: 95-98%
- • Older motors: 80-90%
- • Variable frequency drives: +2-5%
Important Considerations
Starting Current:
- Motors draw 3-8x rated current at start
- Soft starters reduce inrush current
- Consider starting characteristics
Safety Factors:
- Wire ampacity: 125% of motor current
- Breaker rating: 250% for starting
- Continuous duty considerations