vavg vrms
nishant22,
RMS voltage for a given waveform is the voltage that produces the same heating effect in a resistive load as a DC voltage with the same value. As subharpe mentioned, its relationship to the average value depends on the waveform. For example, for a sine wave, the RMS voltage is approximately 1.1 X the average value and is equal to .707 X the peak value. For a symmetrical square wave, the peak, average and RMS values are equal.
Regards,
Kral