Ohms law is not that complicated, we always know at least two of the variables, so it becomes easy to calculate the remaining two.
V = I x R (V=voltage, I = current (in amps), R=resistance (ohms))
P = I x V (P=Power (watts))
I = V/R
The Voltage never changes from 4.2v unless you are using a stacked tube or series mech, in which case you simply multiply 4.2 by the number of batteries you have in your device.
Equations can be off putting so:
If you want to know what amps you’ll be pulling from the battery when you fire it: 4.2 / Coil resistance. For example, 4.2 / 0.22 = 19 amps (This applies to single battery tube mods and parallel mods). This is very important as it helps to identify whether your build will be within the range of your batteries continuous discharge rate (CDR) when you fire it.
For power multiply your amps from the previous calculation by 4.2. So it’s 4.2 x 19 = 80.18w. Therefore a single cell mech running a 0.22ohm build would pull 19 amps from the battery and be vaping at 80.18 watts.
Some examples are given below:
| Resistance (Ohms) | Power (Watts) | Current (Amps) |
| 0.25 | 70.56W | 16.8A |
| 0.24 | 73.50W | 17.5A |
| 0.23 | 76.70W | 18.2A |
| 0.22 | 80.18W | 19.0A |
| 0.21 | 84.00W | 20.0A |
| 0.2 | 88.20W | 21.0A |
| 0.19 | 92.84W | 22.1A |
| 0.18 | 98.00W | 23.3A |
| 0.17 | 103.7W | 24.7A |
| 0.16 | 110.2W | 26.2A |
| 0.15 | 117.6W | 28.0A |
| 0.14 | 126.0W | 30.0A |
| 0.13 | 135.6W | 32.3A |
| 0.12 | 147.0W | 35.0A |