# Mains voltage

- UK mains voltage is 230V
*RMS value* *RMS*means*root mean square*- the
*RMS value*is calculated from a*peak value* - the
*peak value*is the same as the*amplitude*of the wave - the
*peak value***isn’t the same**as the*peak-to-peak value* - the
*RMS value*depends on the*shape of the wave* - for a
*sinusoid*, the*RMS value*is about`0.707`

of its*peak value* - the coefficient comes from
`1/√2 ≈ 0.707`

Thus:

- taking the
*RMS value*of`230V`

`230V / 0.707 ≈ 325V`

; that’s the*peak value*(or the*amplitude*)- the
*peak-to-peak value*is twice that, at`650V`