THE NUMORIX GUIDE
How to use the Ohm's Law Calculator
Last reviewed September 14, 2026
What this calculator does
The UI offers V & I, V & R, and I & R modes.
Formula and method
The UI offers V & I, V & R, and I & R modes. It applies Ohm's law, V = I*R: from voltage and current it derives R = V/I, from voltage and resistance it derives I = V/R, and from current and resistance it derives V = I*R. It also reports electrical power as P = V*I, with derived values rounded to four decimals by the engine.
Variables and inputs
Enter voltage in volts, current in amperes, or resistance in ohms, according to the selected pair. The visible handler requires both entered values to be positive and numeric; the result includes V, I, R, and power in watts. There is no unit conversion or AC phase input.
Worked example
In V & I mode with 12 V and 2 A, resistance is R = 12/2 = 6 ohms and power is P = 12*2 = 24 W. The result card therefore shows 12 V, 2 A, 6 ohms, and 24 W.
How to interpret the result
The calculation describes a component whose voltage, current, and resistance follow a linear relationship at the operating point. Power is the rate of electrical energy transfer, so the same voltage and current also identify how much energy per second the component receives.
Common mistakes to avoid
Use the voltage across the component and the current through it, not a supply rating and a circuit-wide current from unrelated points. Keep volts, amperes, and ohms consistent, and do not treat resistance in ohms as a measure of energy or power.
Assumptions and limitations
The model is an ideal DC resistance calculation and does not include temperature-dependent resistance, non-ohmic devices, internal source resistance, wiring losses, or reactive impedance. The UI blocks zero inputs, although the engine has separate infinity behavior for zero current or resistance paths.