Watts to Amps Calculator
Convert electrical power in watts or kilowatts to current in amps for DC, single-phase AC, and three-phase AC circuits.
Calculator Inputs
Current Result
How to use this calculator
- Select the circuit type. Choose direct current (DC), single-phase AC, or three-phase AC depending on your power source.
- Enter the power and voltage. Type the power value in watts (W) or kilowatts (kW), followed by the supply voltage in volts (V).
- Set the power factor (AC only). For AC circuits, enter the operating power factor between 0.01 and 1.0 (defaults to 1.0 for purely resistive loads).
- Read the current. The resulting current in amps (A) is computed instantly.
Formulas
The relationship between power and current depends on the circuit type:
- Direct Current (DC): I = P / V
- AC Single Phase: I = P / (V × PF)
- AC Three Phase (Line-to-Line): I = P / (√3 × V × PF)
Where P is power in watts, V is voltage in volts, I is current in amps, and PF is power factor.
Worked Example
Convert a 2300 W electric kettle running on a 230 V single-phase AC circuit with PF = 1.0:
- Formula: I = P / (V × PF)
- Calculation: I = 2300 / (230 × 1.0) = 10 A
The kettle draws 10 amps of current under full load.
Frequently Asked Questions
What is the formula to convert watts to amps for DC circuits?
For DC circuits, divide the power in watts by the voltage: I = P / V. For instance, a 120 W load on a 12 V battery draws 10 A.
Why does AC conversion require a power factor?
In alternating current circuits with inductive or capacitive components, voltage and current waveforms can be out of phase. The power factor (PF) accounts for this phase difference.
What power factor should I enter if I do not know it?
For resistive equipment like electric heaters or incandescent lights, the power factor is 1.0. For typical electric motors or general inductive loads, 0.8 to 0.9 is a common operating estimate.
Which voltage do I enter for a three-phase system?
Enter the line-to-line RMS voltage (such as 400 V or 480 V), not the phase-to-neutral voltage. The three-phase formula already incorporates the square root of 3 (approximately 1.732).
Can I convert kilowatts directly with this calculator?
Yes. The calculator accepts power in either watts (W) or kilowatts (kW) and automatically converts as needed.
How does current affect cable sizing?
Current in amps determines how much heat the conductor produces and how much voltage will be lost along the run.
Disclaimer
This calculator is provided for educational and estimation purposes only. Always consult a licensed electrical professional and adhere to your local electrical codes and standards before making any decisions based on these calculations.
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