If a voltmeter measures a sine wave as 500 mV, what would be its average value?

Some AC Voltage Conversion:

Peak to rms: multiply peak by 0.707.

Peak to average: multiply peak by 0.637.

Rms to peak: multiply rms by 1.414.

Rms to average: multiply rms by 0.9.

Average to rms: multiply avg by 1.111.

Average to peak: multiply avg by 1.567.

Mostly voltmeter shows rms value. So, Vav = 0.9*Vrms

= 0.9*500.

= 450mV ~ [D] 451 mV.