RMS Voltage Calculator

The peak voltage equals the RMS times the square root of two, so Vpeak = Vrms x 1.41421. Entering 120 V RMS returns about 169.7056 V peak, and 230 V RMS returns about 325.2691 V peak.

Divide the peak by the square root of two, Vrms = Vpeak / 1.41421. A 170 V peak gives about 120.2082 V RMS, which is why a nominal 120 V outlet crests near 170 V on each half cycle.

Peak-to-peak is the full swing from the negative crest to the positive crest, Vpp = 2 x Vpeak. For a 170 V peak the peak-to-peak voltage is 340 V, and it is what you typically read off an oscilloscope grid.

It is the full-wave rectified mean, Vavg = 2 x Vpeak / pi, which is about 0.637 of the peak. The plain average of an unrectified sine over a whole cycle is zero, since the positive and negative halves cancel.

Enter whichever one you actually measured. Use RMS for a multimeter reading, peak or peak-to-peak for an oscilloscope trace, and average when a spec sheet quotes rectified mean. The calculator derives the other three from that single input.

Yes. The square root of two and 2 over pi factors are specific to a pure sinusoid. Square, triangle, sawtooth and distorted waveforms have different crest and form factors, so this tool would give wrong figures for them.

The tool expects a positive magnitude for the amplitude of an AC waveform. A zero or negative entry is rejected with a prompt to enter a positive voltage, because the conversions describe the size of the swing, not its instantaneous sign.

The engine computes to nine decimal places internally and the display rounds to four, so the small differences you see, such as 108.2254 versus 108.038, come from genuine rounding rather than error.

No. The whole conversion runs in your browser with plain arithmetic, so the voltages you enter stay on your device and nothing is uploaded.