RMS Voltage Converter

Enter any one of RMS, peak, peak-to-peak, or average — get the others, for sine, square, and triangle waveforms.

Waveform

RMS V

Peak (V_p) V

Peak-to-peak V

Average (rectified) V

Enter any one value; the rest are computed for the selected waveform. "Average" is the rectified mean (the value an averaging multimeter actually measures).

What RMS actually means

The root-mean-square voltage of a waveform is the DC voltage that would dissipate the same power in a resistor. That is why RMS is the number that matters for heating, power, and "how big is this signal" questions: 230 V RMS mains delivers exactly the power that 230 V of DC would. Peak and peak-to-peak, by contrast, describe the extremes the waveform reaches — useful for checking headroom, breakdown voltage, and what your oscilloscope shows.

The conversion factors

Every relationship here is a fixed multiple of the peak value V_p, and the multiple depends on the wave shape:

Waveform	RMS	Average (rectified)	Peak-to-peak
Sine	V_p/√2 = 0.707 V_p	2V_p/π = 0.637 V_p	2 V_p
Square	V_p	V_p	2 V_p
Triangle	V_p/√3 = 0.577 V_p	V_p/2 = 0.500 V_p	2 V_p

Mains example

European mains is 230 V RMS. Its peak is 230 × √2 = 325 V, and its peak-to-peak swing is 650 V — which is why insulation and capacitor voltage ratings have to be chosen for the peak, not the RMS figure. A 325 V peak rectified and smoothed gives roughly that DC bus voltage.

Why cheap multimeters get it wrong

Many inexpensive meters are "average-responding, RMS-calibrated": they actually measure the rectified average and multiply by 1.11, the ratio that converts a sine's average to its RMS. On a sine that is exact, but on a square or triangle wave — or a distorted or clipped signal — the average-to-RMS ratio is different, and the reading is wrong. A "true RMS" meter integrates the square of the waveform and gets it right regardless of shape. The crest factor (peak ÷ RMS) is 1.41 for a sine, 1.00 for a square, and 1.73 for a triangle.

Related tools: the decibel calculator works in voltage ratios that are almost always RMS, and the frequency & period calculator handles the timing axis of the same waveforms.