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Ohm's law calculator
Enter any two of voltage, current, resistance, or power and get the other two instantly — the everyday math of wiring and troubleshooting.
Enter any two values — the other two are calculated.
Enter any two values to solve the circuit.
The relationships
Ohm's law ties voltage (V), current (I), and resistance (R) together; the power (P) formulas fall out of it. From any two quantities you can derive the rest:
V = I × R · I = V ÷ R · R = V ÷ I
P = V × I · P = I² × R · P = V² ÷ R
Units are volts (V), amps (A), ohms (Ω), and watts (W). This covers DC and resistive AC circuits; reactive AC loads also involve power factor and impedance.