dual coil question

[jimi6065]

I have been looking on this forum for an answer to a question about dual coils but couldn't find a clear answer. Can someone please tell me what the standard wattage and voltage would be for a dual coil of 1.8 ohms? I understand that for single coils, it is suggested to add 2 volts to the ohms, but is this formula the same for dual coils, or would I have to add more power since it has 2 coils instead of one? I have been vaping a 1.8 ohm dual coil at 4.8 volts but this seems to burn out the coil very fast (less than 10ml of juice). Also, can someone please explain to me the conversion of watts to volts? How many watts would I need to use to get an equivalent of say 3.8 volts? Thanks a lot.