This HP to Amps calculator helps you convert horsepower (HP) to electrical current (amps) based on voltage, efficiency, and power factor. This tool is essential for electricians, engineers, and DIY enthusiasts working with motors and electrical systems.
HP to Amps Calculator
How to Use the HP to Amps Calculator
Follow these steps:
- Enter Horsepower (HP) – Input the motor’s rated horsepower (e.g., 5 HP).
- Input Voltage (V) – Provide the system’s voltage (e.g., 120V, 240V, or 480V).
- Set Efficiency (%) – Most motors have 80-95% efficiency (default is 90%).
- Enter Power Factor (0-1) – Typically 0.8 to 0.95 for AC motors (default is 0.85).
- Click "Calculate Amps" – Instantly get the current in amperes.
How to Convert HP to Amps
The Basic Formula
For single-phase AC motors:
Amps = (HP × 746) ÷ (Voltage × Efficiency × Power Factor)
For three-phase AC motors:
Amps = (HP × 746) ÷ (Voltage × Efficiency × Power Factor × 1.732)
Where:
- HP = Horsepower
- 746 = Conversion factor (1 HP = 746 watts)
- Voltage = Circuit voltage (120V, 240V, 480V, etc.)
- Efficiency = Motor efficiency (typically 0.8 to 0.95)
- Power Factor = Ratio of real power to apparent power (typically 0.8 to 0.95)
- 1.732 = √3 (three-phase conversion factor)
Step-by-Step Conversion
1. Gather Motor Specifications
- Horsepower rating (from motor nameplate)
- Voltage (system voltage)
- Efficiency (if unknown, use 85% or 0.85)
- Power Factor (if unknown, use 0.85)
2. Choose the Correct Formula
- Single-phase motors: Use basic formula
- Three-phase motors: Include the 1.732 factor
Example
Convert 5 HP to amps at 240V (three-phase):
Amps = (5 × 746) ÷ (240 × 0.85 × 0.85 × 1.732)
= 3,730 ÷ 300
= 12.43 amps
HP to Amps Conversion Chart
(Assumes 90% efficiency and 0.85 power factor for AC motors.)
| HP | 120V (Single-Phase) | 240V (Single-Phase) | 480V (Three-Phase) |
|---|---|---|---|
| 1/4 HP | 2.4 A | 1.2 A | 0.6 A |
| 1/3 HP | 3.2 A | 1.6 A | 0.8 A |
| 1/2 HP | 4.8 A | 2.4 A | 1.2 A |
| 3/4 HP | 7.2 A | 3.6 A | 1.8 A |
| 1 HP | 9.6 A | 4.8 A | 2.4 A |
| 1.5 HP | 14.4 A | 7.2 A | 3.6 A |
| 2 HP | 19.2 A | 9.6 A | 4.8 A |
| 3 HP | 28.8 A | 14.4 A | 7.2 A |
| 5 HP | 48.0 A | 24.0 A | 12.0 A |
| 7.5 HP | 72.0 A | 36.0 A | 18.0 A |
| 10 HP | 96.0 A | 48.0 A | 24.0 A |
| 15 HP | 144.0 A | 72.0 A | 36.0 A |
| 20 HP | 192.0 A | 96.0 A | 48.0 A |
| 25 HP | 240.0 A | 120.0 A | 60.0 A |
| 30 HP | 288.0 A | 144.0 A | 72.0 A |
| 40 HP | 384.0 A | 192.0 A | 96.0 A |
| 50 HP | 480.0 A | 240.0 A | 120.0 A |
FAQs
1. How many amps is 1 HP?
1 HP motor typically draws
- 8.1 A at 120V (single-phase)
- 4.8 A at 240V (single-phase)
- 2.4 A at 480V (three-phase)
2. How many amps is 50 HP?
50 HP motor draws approximately:
- ~480 A at 120V (single-phase)
- ~240 A at 240V (single-phase)
- ~120 A at 480V (three-phase)
3. How many amps is 1.5 HP at 220V?
1.5 HP motor at 220V (single-phase) draws about 7.2 A (assuming 88% efficiency and 0.8 power factor).
Also see: Energy Converters