RMS Voltage Calculator (Peak, Peak-to-Peak and Average)
Choose the waveform, say which value you know, and enter it. The calculator gives all four amplitudes (RMS, peak, peak-to-peak and average) plus crest and form factor. It works for volts or amps and assumes no DC offset.
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Formula
With peak value Vp and no DC offset:
| Waveform | RMS | Average (rectified) | Crest factor | Form factor |
|---|---|---|---|---|
| Sine | Vp / √2 |
2 Vp / π |
√2 = 1.4142 |
1.1107 |
| Square | Vp |
Vp |
1 |
1 |
| Triangle | Vp / √3 |
Vp / 2 |
√3 = 1.7321 |
1.1547 |
Peak-to-peak is always 2 × Vp. Whichever value you enter is first converted to the peak value.
Worked example
A 230 V RMS sine wave: Vp = 230 × √2 = 325.27 V, peak-to-peak 650.54 V, rectified average 2 × 325.27 / π = 207.07 V.
A 10 V peak triangle wave: RMS 10 / √3 = 5.7735 V, average 5 V.
Frequently asked questions
How do you convert RMS to peak for a sine wave?
Peak = RMS × √2 = RMS × 1.4142. A 230 V RMS mains sine wave peaks at 230 × 1.4142 = 325.27 V, and its peak-to-peak value is 650.54 V.
What are the RMS factors for square and triangle waves?
A symmetric square wave has RMS = peak. A triangle wave has RMS = peak ÷ √3 = 0.5774 × peak, so a 10 V peak triangle is 5.77 V RMS.
What does average mean for an AC wave?
A symmetric wave averages to zero over a full cycle, so the average here is the rectified (absolute-value) average. For a sine it is 2 ÷ π × peak = 0.6366 × peak, so a 170 V peak sine averages 108.23 V.
Why does a multimeter reading differ from these numbers?
Many cheap meters measure the rectified average and scale it by 1.1107 to show RMS, which is only correct for a sine wave. Square and triangle waves read wrong unless the meter is true-RMS. These results are for learning and design checks, not safety certification.