Are you using a mechanical or regulated mod?
With a
mechanical mod, coil resistance is relevant so you use Ohm's Law.
Explain it to the Dumb Noob: Ohm's Law Calculations for a Mechanical Mod
3.7 volts is the nominal or average voltage of a battery; 4.2 volts is the voltage of a fully charged battery. We generally use 4.2 volts in the Ohm's Law calculations.
With a
regulated mod, coil resistance is irrelevant. What is relevant is the
wattage setting that you use. You now use Watt's Law.
WATTAGE PER SINGLE BATTERY on REGULATED MOD:
(wattage doubles when using 2 batteries/triples when using 3 batteries)
Up to 45W:
Samsung 18650 30Q, 3000 mah 15 amp CDR
Sony 18650VTC6 3000mAh 15 amp CDR
Up to 60W:
LG 18650HG2 3000mah 20 amp CDR
LG 18650HE4 2500 mah 20 amp CDR
Samsung 18650-25R, 2500 mah 20 amp CDR
Sanyo UR18650NSX, 2500 mah 20 amp CDR
Sony 18650VTC5, 2600 mah 20 amp CDR
Sony 18650VTC4, 2100 mah 23 amp CDR
AW 18650 3000 mah 20 amp CDR
Up to 75W:
LG 18650 HD4 2100 mah 25 amp CDR
LG 18650 HD2 2000 mah 25 amp CDR
Samsung 18650-24S, 2500 mah 25 amp CDR
Sony 18650VTC5A, 2500 mah 25 amp CDR
Up to 90W:
LG18650HB6 1500mah 30 amp CDR
LG18650HB2 1500mAh 30 amp CDR
LG18650HB4 1500mAh 30 amp CDR
Samsung 18650-20S 2000mah 30 amp CDR