What formula is used for DC circuits?

V = (HP × 746) / (A × Eff). One horsepower equals 746 watts; dividing output watts by current and efficiency gives the required voltage.

What formula is used for single-phase AC circuits?

V = (HP × 746) / (A × PF × Eff). The power factor reduces the effective power drawn, so a higher voltage is required compared to DC for the same current and HP.

What formula is used for three-phase AC circuits?

V = (HP × 746) / (√3 × A × PF × Eff). The √3 factor (≈ 1.7321) reflects the three-phase line-to-line voltage relationship. The result is the line-to-line voltage.

Why is 746 used in these formulas?

One mechanical horsepower is defined as approximately 745.7 watts, conventionally rounded to 746 W. This conversion factor links mechanical and electrical power units.

What is a typical power factor for electric motors?

Most induction motors operate at a power factor between 0.75 and 0.95 under full load. Lightly loaded motors can have lower power factors. The nameplate or datasheet will specify the rated value.

What efficiency value should I use?

Standard motors typically achieve 85–95% efficiency. Premium-efficiency motors can exceed 95%. Use the value from the motor nameplate or datasheet for accurate results.

Does this tool account for starting current or inrush?

No. This calculator uses steady-state (running) values. Starting current can be 6–8 times the running current and must be handled separately when selecting circuit breakers or contactors.

Horsepower to Volts Calculator

Name: Horsepower to Volts Calculator
Availability: InStock
Author: Nham Vu

Convert horsepower (HP) to volts for DC, single-phase AC, or three-phase AC circuits by entering current, efficiency, and power factor.

Circuit Parameters

Circuit Type

Horsepower (HP)

Current (A)

Motor Efficiency (%) (1 – 100)

Result

Enter values and press Calculate

Formula Reference

DC Circuits

V = (HP × 746) / (A × Eff)

Single-Phase AC

V = (HP × 746) / (A × PF × Eff)

Three-Phase AC

V = (HP × 746) / (√3 × A × PF × Eff)

Result copied!

Summary

Convert horsepower (HP) to volts for DC, single-phase AC, or three-phase AC circuits by entering current, efficiency, and power factor.

How it works

Select your circuit type: DC, single-phase AC, or three-phase AC.
Enter the mechanical power in horsepower (HP).
Enter the circuit current in amperes (A).
Enter the motor efficiency as a percentage (typically 85–95%).
For AC circuits, enter the power factor (a value between 0 and 1).
Press Calculate to see the required voltage and a step-by-step breakdown.

Use cases

Determine the supply voltage needed to drive a motor at a given horsepower.
Verify motor nameplate voltage against calculated circuit requirements.
Size power supplies or transformers for motor-driven equipment.
Convert motor specifications from HP to electrical parameters for procurement.
Cross-check wiring diagrams when the voltage rating is missing from documentation.
Design HVAC, pump, or conveyor systems by working backward from mechanical output.
Compare DC and AC supply options for the same mechanical load.
Estimate voltage drop impact on motor output in industrial installations.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu