Calculate voltage, current, resistance, and power from any two known values. Visual circuit diagram updates with computed values.
This calculator completes the four-value Ohm's law set for a single load. Supply any two of voltage, current, resistance, and power, and it derives the remaining two while updating a circuit diagram with the values. It is especially useful when the known pair is not voltage and resistance, such as current plus power. The frequent mistake is mixing values from different operating conditions. All four results must describe the same load at the same operating point, or the equations may reconcile numerically without describing the real circuit.
A concrete input and expected output from the current implementation.
Input
Voltage = 12 V Resistance = 6 ohms
Expected output
Current = 2 A Power = 24 W
Current follows from I = V / R = 12 / 6 = 2 A. Power is P = V * I = 12 * 2 = 24 W; checking with P = V^2 / R also gives 144 / 6 = 24 W.
Select any two distinct known quantities and enter their values. With voltage V, current I, resistance R, and power P, the calculator completes the set from V = I * R and P = V * I. The applicable rearrangement depends on the selected pair. For R and P, the magnitude equations are V = sqrt(P * R) and I = sqrt(P / R).
After calculation, the supplied and derived quantities are shown together on the circuit diagram. This helps identify a result by its electrical symbol: V is voltage, I is current, R is resistance, and P is power. The drawing summarizes one electrical operating point; it does not represent wiring topology, multiple loads, or behavior changing over time.
Any two different quantities among V, I, R, and P determine the other two for positive, nonzero resistive values. For example, R and P determine I from sqrt(P / R), while I and P determine V from P / I. Two entries for the same quantity do not provide two independent equations.
Not for a general AC circuit. The result can be meaningful for a purely resistive load when voltage and current are expressed consistently, often as RMS magnitudes. It does not account for reactance, phase angle, apparent power, or power factor, so it cannot replace an impedance or AC power calculation for reactive loads.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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