01
Choose a direction
Calculate horsepower from electrical values or estimate current from motor horsepower.
Electrical motor power workspace
Electrical Horsepower Calculator
Convert voltage and current into electrical horsepower, or estimate motor current from horsepower. Supports DC, single-phase AC, and three-phase AC systems with efficiency and power factor adjustments.
DC and AC systems
Two-way calculation
Motor efficiency
Power factor support
Horsepower Workbench
Select the calculation direction and electrical system type.
DC motor power calculation
DC Electrical Horsepower
Calculate usable mechanical horsepower from DC voltage, current, and motor efficiency.
HP = V × I × η ÷ 745.7
How it works
Calculate Electrical Horsepower in Four Steps
The calculator converts all values to base electrical units, applies the correct DC or AC formula, includes efficiency, and displays horsepower, current, power, and losses.
02
Select the system
Choose DC, single-phase AC, or three-phase AC according to the electrical supply.
03
Enter motor values
Add voltage, current or horsepower, efficiency, and AC power factor where required.
04
Review the output
See horsepower or current along with electrical input, mechanical output, and estimated losses.
Motor power fundamentals
Understanding Electrical Horsepower
Electrical horsepower is a way to express electrical or mechanical power using horsepower units. One mechanical horsepower is approximately 745.7 watts.
A motor does not normally convert all incoming electrical power into useful mechanical output. Some energy is lost through heat, winding resistance, friction, magnetic losses, and ventilation. Motor efficiency accounts for these losses.
AC motors also require a power factor adjustment. Power factor describes how effectively apparent electrical power is converted into real power.
Efficiency changes output horsepower
Lower motor efficiency means less mechanical
output from the same electrical input.
Power factor applies to AC systems
Single-phase and three-phase motors require
power factor for a more realistic estimate.
Starting current can be much higher
Calculated current represents an operating
estimate and not motor starting or locked-rotor
current.
Electrical Horsepower Formulas
DC motor horsepower
HP = V × I × η ÷ 745.7
V is voltage, I is current, and η is efficiency as a
decimal.
Single-phase AC horsepower
HP = V × I × PF × η ÷ 745.7
PF is the AC power factor expressed as a decimal.
Three-phase AC horsepower
HP = √3 × V × I × PF × η ÷ 745.7
The voltage should normally be line-to-line voltage.
Horsepower to watts
Watts = HP × 745.7
Mechanical output watts are divided by efficiency to
estimate required electrical input power.
Practical uses
Where Horsepower Calculations Are Useful
Electrical horsepower calculations help with motor selection, circuit planning, load estimates, troubleshooting, and industrial power analysis.
Industrial Motors
Estimate horsepower and current for pumps, fans, compressors, and production equipment.
HVAC Equipment
Review electrical requirements for blowers, cooling fans, and compressor motors.
Pump Systems
Convert pump motor electrical data into estimated usable mechanical horsepower.
Circuit Planning
Estimate operating current before selecting wiring, protective devices, and power supplies.
Motor Troubleshooting
Compare measured voltage and current against expected horsepower and power consumption.
Electrical Learning
Understand the relationship between watts, horsepower, efficiency, current, and power factor.
Frequently asked questions
Electrical Horsepower Calculator FAQs
Common questions about converting electrical power to horsepower, motor current, efficiency, and power factor.
How do I calculate electrical horsepower?
For a DC circuit, multiply voltage by current and motor efficiency, then divide by 745.7. AC calculations also include power factor, and three-phase calculations use the square root of three.
How many watts are in one horsepower?
One mechanical horsepower is approximately 745.7 watts. Many simplified electrical calculations round this value to 746 watts.
Why is motor efficiency included?
Motors lose some electrical energy through heat, friction, winding resistance, magnetic losses, and ventilation. Efficiency estimates the portion converted into useful mechanical output.
What power factor should I use?
Use the power factor listed on the motor nameplate or manufacturer documentation. When it is unknown, a reasonable estimate may be used, but the result will be less precise.
What is the three-phase horsepower formula?
Three-phase horsepower equals the square root of three multiplied by line voltage, current, power factor, and efficiency, divided by 745.7.
Can this calculator estimate motor current?
Yes. Select HP to Current, choose the electrical system, and enter horsepower, voltage, efficiency, and power factor where required.
Is calculated current the motor starting current?
No. The result is an estimated operating current. Starting current or locked-rotor current can be several times higher and should be checked using motor data.
Should I use line voltage for three-phase power?
Yes. This calculator uses the standard three-phase formula based on line-to-line voltage and line current.
Are the results suitable for wire or breaker sizing?
The result is an engineering estimate only. Final wire, breaker, overload, and motor protection selections should follow equipment data and applicable electrical codes.
Electrical design reminder:
This calculator provides estimated operating values. Actual motor
current can vary because of load, efficiency, power factor,
voltage variation, temperature, motor design, and starting
conditions. Always verify equipment nameplate data.