RMS Voltage Calculator

About this calculator

For a sinusoidal AC voltage, this calculator finds the RMS (root-mean-square) voltage, Vrms = Vpeak / √2 (≈ 0.707 × Vpeak), and the peak-to-peak voltage, Vpp = 2 × Vpeak. RMS voltage is the value that would deliver the same average power to a resistive load as an equivalent DC voltage — it's derived by squaring the sine wave, averaging over a full cycle, and taking the square root.

RMS is the standard way AC voltage is specified everywhere: a "230V" or "120V" mains outlet is an RMS value, not the actual peak voltage (which is roughly 325V or 170V respectively), and RMS current and voltage are what's used to calculate real power dissipation, P = Vrms × Irms, in any AC circuit.

Electrical engineers and electricians sizing wiring and components for AC power, audio engineers working with amplifier voltage specs, and electronics students converting between peak, peak-to-peak, and RMS readings on an oscilloscope all use this calculator.