AC RMS and Peak Calculator
Convert peak magnitude to RMS, peak-to-peak and crest factor for three ideal waveforms.
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Convert ideal waveform peak into practical amplitude measures
Select a zero-centered sine, square or triangle waveform and enter its nonnegative peak magnitude. The calculator reports RMS magnitude, peak-to-peak magnitude and crest factor. This keeps waveform shape explicit: identical peaks do not imply identical heating-equivalent RMS values, and the familiar square-root-of-two conversion belongs to a sine wave rather than every alternating signal.
Use sampled RMS for arbitrary or offset waveforms
Distortion, duty-cycle changes, transients and DC offset alter RMS and crest factor. A meter can also have bandwidth and true-RMS limits. For a real nonideal signal, calculate the square root of the mean squared samples over a representative interval and verify the instrument method. This page does not infer power without load and phase information.
Frequently asked questions
Why does waveform shape change RMS?
RMS depends on how the squared magnitude is distributed over a full cycle.
Is peak-to-peak always twice peak?
Yes for the ideal symmetric zero-centered waveforms offered here.
Can this calculate an arbitrary measured waveform?
No. Use representative samples and a sample-based RMS calculation.