We should know the input voltage (Vrms) and the required output voltage (Vreq) and current (Iout). 2. Calculate the impedance (Z). Z=((Vrms X 1.41) - Vreq) / Iout 3. Calculate the required Capacitance (C) value. C =1/ (2 X 3.14 X frequency X Z) I have explained in details in the tutorial video.