Ohm's law & power calculator
Interactive engineering and procurement calculator. Instant client-side computation with no sign-up.
Known values
Enter any two of V, I, R and P.
Results
Voltage (V)
Entered
Current (I)
Entered
Resistance (R)
R = V ÷ I
Power (P)
P = V × I
The V·I·R·P wheel
The same four quantities — pick the two you know, read the one you want.
| Solve for | Formulas |
|---|---|
| V · voltage | I × R · P ÷ I · √(P × R) |
| I · current | V ÷ R · P ÷ V · √(P ÷ R) |
| R · resistance | V ÷ I · V² ÷ P · P ÷ I² |
| P · power | V × I · V² ÷ R · I² × R |
About the model
Ohm's law ties voltage, current and resistance: V = I × R. The power equations follow straight from it — P = V × I, and substituting V = I × R gives P = I² × R, or P = V² ÷ R. Any two of the four determine the other two, as long as the values are consistent.
This is the linear, DC model — right for a resistor, an LED current path or a fixed load. Real parts drift with temperature and frequency, and a thermistor or an inductor breaks the simple ratios.
Picking the parts? Browse chip resistors and resistor networks, current-sense resistors or fuses in the catalog.
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