Wattage to Amperage Calculator
Convert watts to amps for DC and AC circuits using voltage, power factor, and phase type.
Converting Wattage to Amperage
Electrical appliances list power in watts, but circuit breakers and wire sizing require current in amps. This calculator converts power and voltage into current for DC, single-phase AC, and three-phase AC circuits.
Formulas
DC circuit:
$$I = \frac{P}{V}$$AC single-phase:
$$I = \frac{P}{V \times PF}$$AC three-phase (line-to-line voltage):
$$I = \frac{P}{\sqrt{3} \times V \times PF}$$AC three-phase (line-to-neutral voltage):
$$I = \frac{P}{3 \times V \times PF}$$\(P\) is power in watts, \(V\) is RMS voltage, \(I\) is current in amps, and \(PF\) is power factor.
Example
A 1500 W appliance on a 120 V DC circuit draws \(1500 / 120 = 12.5\) A. On a 120 V single-phase AC circuit with power factor 1, the current is also 12.5 A.
Related tools: Watts to Amps Calculator and Amps to Watts Calculator.
Frequently Asked Questions
What is the difference between wattage and amperage?
Wattage (power) measures how much energy is used per second. Amperage (current) measures how many electrons flow through a conductor. Voltage links them: P = V × I for DC circuits.
When do I need power factor?
Power factor is required for AC circuits. DC circuits have a power factor of 1. Inductive loads like motors typically have power factors between 0.8 and 0.95.
What voltage should I use for three-phase?
Use line-to-line voltage (e.g., 480 V) or line-to-neutral voltage (e.g., 277 V) depending on how your system is wired. Select the matching option in the calculator.
Can I size a breaker with this result?
Use this as a starting estimate. Final breaker and wire sizing must follow applicable electrical codes with appropriate safety margins.
Is RMS voltage the same as peak voltage?
No. RMS (root mean square) voltage is what most meters and nameplates report. Peak voltage is higher by a factor of √2 for sinusoidal AC.
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