Volts / Amps / Watts

Enter any two values to solve the third instantly. Includes unit conversions and Show Work.

How to Use

  1. Enter any two values: Voltage (V), Current (I), or Power (W).
  2. Select the correct units (mA, kW, etc.).
  3. Optionally choose “Solve For” to force the output variable.
  4. Open “Show Work” to see the formula and steps in base units.
Power Triangle
Live feedback: V × I = W
V
—
I
—
W
—
Load: —
W V I W = V × I V = W ÷ I I = W ÷ V Tip: Use Auto-scale outputs for readable mA/kW formatting.
Inputs & Settings
Type any two values. Choose “Solve For” if you want to force an output.
Common: 5V, 12V, 14.4V, 120V, 230V
Examples: 20mA LED, 2A USB, 10A+ automotive
Use for load sizing, fusing estimates, and heat guidance
If AC mode is selected, real power W = V × I × PF
Show Work (step-by-step)
—
Work is shown in base units (V, A, W) and PF when applicable.

Formulas

Core relationship: W = V × I (DC / resistive loads).

  • Watts: W = V × I
  • Volts: V = W ÷ I
  • Amps: I = W ÷ V
  • AC (optional): W = V × I × PF
Where V = volts, I = amps, W = watts, PF = power factor (0–1).

FAQ

What if I only know one value?

You need at least two of the three (V, I, W) to solve the missing one.

Why does AC have a Power Factor option?

For many AC loads, real power is lower than V × I. Power factor accounts for phase shift and non-ideal waveforms.

Is this the same as Ohm’s Law?

This tool is the power relationship triangle. Ohm’s Law adds resistance: V = I × R. You can combine them when R is known.

What’s a quick car example?

A 12V accessory pulling 10A uses about 120W (DC). Heat and fuse sizing should consider real-world wiring limits.

Tool Info

Last updated:

Updates may include UI improvements, unit support, and calculation edge-case handling.