HP to AMPS Calculator

What Is HP to AMPS Conversion?

Horsepower (HP) measures mechanical power. Amps (A) measure electrical current. Motors convert electrical power into mechanical power, but the conversion is never perfect. Some energy is lost as heat and friction.

That is why you cannot convert HP to amps using a single fixed number. You must consider:

• Voltage
• Motor efficiency
• Power factor (for AC motors)
• Motor type (AC single-phase, AC three-phase, or DC)

The HP to AMPS calculator combines all these values to estimate how much current a motor will draw.

Why This Calculator Is Useful

This calculator is helpful if you:

• Size circuit breakers or fuses
• Select wire size
• Design electrical panels
• Estimate motor load
• Compare current draw at different voltages

It saves time and reduces errors compared to manual calculations.

Inputs Used in the HP to AMPS Calculator

The calculator you shared uses industry-standard inputs. Here is what each one means.

1. Motor Type

You can select:

• AC Single Phase
• AC Three Phase
• DC Motor

Motor type matters because the electrical formulas are different. Three-phase motors draw less current than single-phase motors for the same horsepower.

2. Horsepower (HP)

Horsepower is the motor’s mechanical output power.

The calculator uses this fixed conversion:

1 HP = 746 Watts

Example:
5 HP × 746 = 3,730 Watts

3. Voltage (V)

Voltage is the electrical supply feeding the motor. Common values include:

• 120 V
• 230 V
• 240 V
• 480 V

Higher voltage usually means lower current for the same power.

4. Efficiency (%)

Efficiency shows how much input power is converted into useful output power.

• 90% efficiency means 10% is lost
• Lower efficiency increases current draw

The calculator converts efficiency into decimal form before calculating.

5. Power Factor (AC Motors Only)

Power factor applies only to AC motors.

• Typical values range from 0.7 to 0.95
• A lower power factor increases current
• DC motors do not use power factor

The calculator automatically hides this input when DC is selected.

Formulas Used in the Calculator

The calculator clearly displays the formula used for each motor type. This helps users understand where the numbers come from.

AC Single-Phase Motor Formula

Amps = (HP × 746) ÷ (Voltage × Efficiency × Power Factor)

AC Three-Phase Motor Formula

Amps = (HP × 746) ÷ (Voltage × Efficiency × Power Factor × 1.732)

The value 1.732 comes from the square root of 3 and is standard for three-phase systems.

DC Motor Formula

Amps = (HP × 746) ÷ (Voltage × Efficiency)

Power factor is not used for DC motors.

Additional Results Shown by the Calculator

Besides the main current value, the calculator also displays:

• Power in Watts (W)
• Power in Kilowatts (kW)
• Estimated current at 120 V
• Estimated current at 240 V
• Estimated current at 480 V

This makes it easy to compare how current changes with voltage.

Example Calculation

Let’s use a simple example.

• Motor type: AC Single Phase
• Horsepower: 5 HP
• Voltage: 230 V
• Efficiency: 90%
• Power factor: 0.85

Steps the calculator follows:

1. Convert HP to watts
   5 × 746 = 3,730 W
2. Apply the formula
   Amps = 3,730 ÷ (230 × 0.90 × 0.85)
3. Result
   Approximate current is displayed in amps

The calculator does all this instantly.

Error Handling and Validation

The calculator checks for common input errors:

• Zero or negative values
• Missing efficiency
• Missing power factor for AC motors

If inputs are invalid, the results section shows clear error messages instead of incorrect values.

Important Notes and Limitations

• Results are estimates, not exact values
• Actual motor current depends on load conditions
• Starting current (inrush current) is not included
• Always check motor nameplate data for critical work

For safety-critical applications, consult a licensed electrician.

Who Should Use This Calculator?

This HP to AMPS calculator is ideal for:

• Electricians
• Engineers
• HVAC technicians
• Students and trainees
• DIY users planning electrical loads

It balances accuracy with simplicity, making it useful for both professionals and learners.