How to use the watts / amps / volts converter
The formulas
DC: P = V × I, so I = P ÷ V and V = P ÷ I.
AC single-phase: P = V × I × PF, so I = P ÷ (V × PF) and V = P ÷ (I × PF).
How to use it
Choose DC or AC single-phase at the top. For AC, set the power factor (it appears only in AC mode). Then fill in any two of the three boxes and press Convert.
Where you will use this
Checking whether a circuit can carry a new appliance, sizing a power supply, estimating a solar or battery load, or sanity-checking a nameplate rating — it is the same three-way relationship every time.
Example
A 600 W load on a 120 V AC circuit with power factor 0.8: I = 600 ÷ (120 × 0.8) = 6.25 A. The same load on pure DC at 12 V would draw 600 ÷ 12 = 50 A — which is why low-voltage systems need such heavy cable.
Frequently asked questions
What is the difference between the DC and AC modes?
DC uses P = V × I. Single-phase AC uses P = V × I × PF, because with reactive loads some current does no useful work. That extra factor is the power factor.
What power factor should I use?
Pure resistive loads (heaters, incandescent lamps) are close to 1.0. Motors and many electronic drivers sit around 0.7–0.9; 0.8 is a common planning estimate when the nameplate does not say.
How many amps does a 1,500 W heater draw at 120 V?
At PF 1: 1,500 ÷ 120 = 12.5 A. Try it: choose DC (or AC with PF 1), enter 120 V and 1,500 W.
Why does the nameplate VA differ from watts?
VA (apparent power) is V × I without the power factor. Watts = VA × PF, so on AC a device can draw more current than its wattage alone suggests.
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