Well it depends on how hot and large a coil I'm running. Coils that get hotter or have more surface area use more juice than smaller, cooler coils. Then there's the size of the drops, some droppers make big drops, some small.
Take the Hobo I'm running, the coil I had in it yesterday was 6 wraps at 1.4ohms wicked with silica and I barley had to drip throughout the day. Today I have a 4 wrap 1ohm twisted coil with cotton, feels like I'm am dripping every other hit.