How can you calculate the capacitor used for single phase?

Single phase motor cannot start alone as rotating magnetic flux is not generated with single phase supply.

To make rotating magnetic field in stator single phase supply is made like double phase supply with the help of a capacitor and double phase stator winding.

For a 230V 50Hz motor 50 MF / HP is a rough and ready starting point. i.e. for a 60W motor use 60/750 X 50 = 4 MF.

I am sorry this is out of my specialist !!!