Enter a voltage value and select whether it's a Peak Voltage (Vp), Peak-to-Peak Voltage (Vpp), or Average Voltage (Vavg) — the RMS Voltage Calculator converts it to the equivalent RMS voltage (Vrms) used in AC circuit analysis. You also get the reverse conversions for all three voltage types as secondary outputs.
RMS Voltage (Vrms)
--
Peak Voltage (Vp)
--
Peak-to-Peak Voltage (Vpp)
--
Average Voltage (Vavg)
--
RMS stands for Root Mean Square. RMS voltage is the DC-equivalent voltage of an AC waveform — meaning an AC signal with an RMS value of 10V delivers the same power to a resistive load as a 10V DC source. It is the most useful measure of AC voltage for power calculations.
For a sine wave, RMS voltage equals peak voltage multiplied by 0.7071 (which is 1/√2). So if your peak voltage is 170V, the RMS voltage is 170 × 0.7071 ≈ 120.2V — which is why household mains are described as 120V RMS despite having a peak of about 170V.
Divide the peak-to-peak voltage by 2√2 (approximately 2.8284). The formula is Vrms = Vpp × 0.35355. For example, a 340V peak-to-peak sine wave has an RMS voltage of 340 × 0.35355 ≈ 120.2V.
Multiply the average voltage by π/(2√2), which equals approximately 1.1107. So Vrms = Vavg × 1.1107. Note that the average voltage of a full sine wave is zero; the 'average' used in this context refers to the average of the rectified (absolute value) waveform.
The standard 120V used to describe household electricity in North America is an RMS value, not peak voltage. The actual peak voltage of a 120V RMS supply is about 169.7V, and the peak-to-peak voltage is approximately 339.4V.
Average voltage is simply the arithmetic mean of a waveform's absolute values over one cycle, while RMS voltage is derived from the square root of the mean of the squared values. For a sine wave, Vrms ≈ 1.1107 × Vavg. RMS is preferred for power calculations because it accounts for the energy content of the waveform.
For a pure DC signal, the RMS value equals the DC voltage itself, because the signal does not vary. There is no peak-to-peak variation or waveform shape to account for — the RMS, average, and peak values are all identical.
This calculator uses the standard sine wave formulas (Vrms = 0.7071 × Vp) which are valid for pure sinusoidal AC signals. For other waveform shapes such as square waves, triangle waves, or sawtooth waves, different crest factors apply and the conversion factors will differ.