Motor nameplates often list power in horsepower. Converting to amps tells you which cable, breaker and supply you need. Efficiency and power factor increase the current above the simple P/V value.
How to use the Horsepower to Amps Calculator
- Current type
- Power
- Voltage
- Efficiency (%)
- Power factor
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the current type, enter the horsepower, voltage, efficiency and (for AC) power factor.
Inputs explained
| Field | What to enter |
|---|---|
| Current type | Choose one: DC, AC single-phase, AC three-phase |
| Power | Units: hp, kW, W |
| Voltage | Units: V, kV, mV |
| Efficiency (%) | A number |
| Power factor | A number |
Example values
How the main result changes when Power changes and everything else stays at the example values above:
| Power (hp) | Current (A) |
|---|---|
| 2.5 | 11.2186 |
| 3.75 | 16.8279 |
| 5 | 22.4372 |
| 6.25 | 28.0465 |
| 7.5 | 33.6558 |
| 10 | 44.8744 |
Formula
DC: I = P/(V·η) · 1-phase: I = P/(V·η·PF) · 3-phase: I = P/(√3·V·η·PF), 1 hp = 745.7 W
Worked example
Inputs — Current type: AC single-phase; Power: 5 hp; Voltage: 230 V; Efficiency (%): 85; Power factor: 0.85.
Results — Current = 22.43719 A; Electrical input power = 4,386.46983 W.
Key terms
- Horsepower
- Unit of power, 745.7 W (mechanical).
Frequently asked questions
How many amps is a 1 hp motor at 230 V?
About 4–5 A single-phase, depending on efficiency and PF.
Why does three-phase need less current?
Power is shared over three conductors.
What is a mechanical horsepower?
745.7 W.
Should I size the breaker at this current?
Motors have high starting currents; follow electrical codes.