THE NUMORIX GUIDE
How to use the Power Calculator
Last reviewed September 14, 2026
What this calculator does
The UI offers V & I, I & R, and V & R modes.
Formula and method
The UI offers V & I, I & R, and V & R modes. It calculates electrical power with P = V*I, P = I^2*R, or P = V^2/R as appropriate, and derives the missing voltage, current, or resistance so the result card can show all three quantities.
Variables and inputs
Enter voltage in volts, current in amperes, and resistance in ohms according to the selected pair. The visible handler requires both entries to be positive; the output is power in watts plus the derived circuit values. No AC frequency, phase, or unit conversion is collected.
Worked example
In the default V & I mode, 120 V and 10 A give P = 120*10 = 1,200 W. The same inputs imply R = V/I = 12 ohms, so the equivalent check P = V^2/R also gives 1,200 W.
How to interpret the result
Power is the rate at which electrical energy is transferred or dissipated. In a resistive DC load, a larger voltage or current raises heating and energy use, while resistance determines how those quantities relate.
Common mistakes to avoid
Do not enter watt-hours when the field asks for watts, and do not mix line voltage with current from another circuit. Use the formula matching the selected pair and remember that resistance is not interchangeable with impedance in AC systems.
Assumptions and limitations
The equations assume a steady resistive DC operating point. They omit reactive power, power factor, transients, harmonics, temperature changes, and source or wiring losses; division by zero is not guarded in the engine even though the UI blocks nonpositive entries.