Power Calculator
Calculate electrical power in watts from any two of voltage, current, or resistance. Uses P = VI, P = V²/R, and P = I²R — useful for circuit design and energy estimation.
24 W
How to use the power calculator
Enter voltage and current; the dissipated/delivered power is V × I.
Formula & explanation
P = V × I (DC or RMS for AC). For sinusoidal AC with non-resistive loads, multiply by power factor cos(θ).
Examples
12 V, 2 A → 24 W.
Frequently asked questions
- How do I calculate power in a circuit?
- Multiply voltage by current: P = V × I. A 12 V circuit carrying 2 A dissipates 24 W.
- What is the difference between watts and volt-amps?
- Watts measure real (consumed) power; volt-amps measure apparent power. They are equal only for purely resistive loads — reactive loads have a power factor less than 1.
- How many watts can a standard 15 A, 120 V outlet supply?
- A 15 A outlet at 120 V can supply up to 1,800 W, though NEC guidelines recommend keeping continuous loads below 1,440 W (80% of the breaker rating).
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