A walkthrough, end to end.
- 1
Enter any two of voltage (V), current (A), resistance (Ω), or power (W).
- 2
The calculator returns the other two using V = IR and P = VI.
- 3
Useful for circuits, LEDs, and electronics homework.
Ohm's law and power
V = I × R. P = V × I = I² × R = V² / R. The calculator solves for the missing pair.
What you can do with this.
LED current limiting
Find the resistor needed to drop voltage.
Motor sizing
Estimate current draw from voltage and resistance.
Power dissipation
Compute heat dissipated in a resistor.
Battery life
Convert capacity (Ah) and voltage to watt-hours.
Wire selection
Pick wire gauge from current and length.
Electronics homework
Solve typical problems in seconds.
Power supply sizing
Sum currents to size a PSU.
Ohm's law 2026 — what's current
Foundational; calculator wins for instant solving.
Frequently asked.
Yes — for AC use peak/RMS appropriately. Power factor isn't included here.
Volts (V), amps (A), ohms (Ω), watts (W).
No. All math runs in your browser.
This calculator handles purely resistive loads.