The same as a single coil, but there are two of them. Counter-intuitively, two coils means more wire and
less resistance, so you need to increase the number of wraps on each one.
single coil - 6 wraps of 28g -
1 ohm total resistance
dual coil - 12 wraps of 28g -
1 ohm total resistance
Coil wrapping | Steam Engine | free vaping calculators
If you are referring to how you physically build the deck you will need to specify what RDA you are using.