Watt to Ampere Calculator
Convert power (Watts) to current (Amperes)
How to Use
- Enter the power in watts (W)
- Enter the voltage in volts (V)
- Select the circuit type (DC, AC Single Phase, or AC Three Phase)
- For AC circuits, enter the power factor (default is 0.9)
- Click calculate to see the current in amperes (A)
Understanding Watts to Amperes Conversion
Converting watts to amperes requires understanding the relationship between power, voltage, and current. The formula varies depending on the type of electrical circuit: DC, AC single-phase, or AC three-phase.
Power (P) is measured in watts (W), current (I) is measured in amperes (A), and voltage (V) is measured in volts (V). The relationship is defined by the formula P = V × I for DC circuits.
Conversion Formulas
| Circuit Type | Formula | Description |
|---|---|---|
| DC (Direct Current) | I = P / V | Simple division of power by voltage |
| AC Single Phase | I = P / (V × PF) | Includes power factor in calculation |
| AC Three Phase | I = P / (√3 × V × PF) | Uses square root of 3 for three-phase systems |
Where: I = Current (Amperes), P = Power (Watts), V = Voltage (Volts), PF = Power Factor (0.01 to 1)
Understanding Power Factor
Power factor (PF) is a dimensionless number between 0 and 1 that represents the efficiency of an AC circuit. A power factor of 1 means all power is being effectively used, while lower values indicate some power is wasted.
- Resistive loads (heaters, incandescent bulbs): PF ≈ 1.0
- Inductive loads (motors, transformers): PF ≈ 0.7-0.9
- Capacitive loads: PF varies
- Mixed loads: PF ≈ 0.8-0.95
- Default typical value: PF = 0.9
Practical Applications
- Sizing electrical wiring and cables for appliances
- Selecting appropriate circuit breakers and fuses
- Calculating electrical load for generators and UPS systems
- Designing electrical distribution panels
- Energy management and load balancing
- Motor and equipment specifications
- Solar panel and battery system design
Safety Considerations
Always ensure that electrical wiring, circuit breakers, and equipment are rated for the calculated current plus a safety margin. Standard practice is to size wiring and breakers for 125% of the continuous load.
Consult with a licensed electrician for electrical installations and modifications to ensure compliance with local electrical codes and safety standards.
Frequently Asked Questions
- How do I convert watts to amperes?
- For DC circuits, divide watts by volts: I = P / V. For AC single-phase, divide watts by (voltage × power factor). For AC three-phase, divide watts by (√3 × voltage × power factor). For example, 1200W at 120V DC equals 10A (1200W / 120V = 10A).
- What power factor should I use?
- For most residential applications, use 0.9 as a typical value. Pure resistive loads like heaters use 1.0, while motors and inductive loads typically range from 0.7 to 0.9. Check equipment specifications for exact values.
- When do I use three-phase calculations?
- Three-phase calculations are used for industrial and commercial electrical systems, large motors, and high-power equipment. Most residential applications use single-phase power. Check your electrical service type if unsure.
- Why is voltage important in this conversion?
- Current is inversely proportional to voltage. Higher voltage results in lower current for the same power. For example, 1200W at 120V draws 10A, but at 240V it only draws 5A. This is why high-power appliances often use higher voltages.