The Formula is Total Nicotine divided by Total Milliliters.
Say you mixed 4ml of 6mg
e-liquid into 5ml of 18mg
e-liquid.
You’d have,
4 times 6mg for the first
e-liquid => 24mg of Nicotine.
and
5 times 18mg for the second e-Liquid => 90mg of Nicotine.
So the Total Nicotine in Both e-Liquids would be 24 + 90 = 114mg Total Nicotine.
And the Total Milliliters would be 4 + 5 = 9ml
Then to figure out what the mg of the e-Liquid would be, Divide 114 (Total Nicotine) by 9 (Total ml) = 12.6mg/ml
So you would end up with 9ml of 12.6mg e-Liquid.