The short answer: Add 8.57 ml of your VG dilution liquid to 30 ml of your 36 mg/ml
juice to make it 28 mg/ml.
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Here's how you can figure that out.
Method #1- the plug and chug (plug in numbers till you get something close to what you want)
You have 30 ml of 36 mg/ml nic. To figure out how many mg of nic are in 30 mls of your
juice multiply:
36 mg/ml * 30 ml = 1080 mg nicotine total.
You want 28 mg/ml nicotine.
Let's see if the example you posted above works out to the right concentration.
You want to take 30 ml of 36 mg/ml and add 3.5 ml of 0 mg/ml.
Your total nicotine is still 1080 mg, but now it's in a total volume of 33.5 ml (30 ml + 3.5 ml):
1080 mg/33.5 ml = 32.2 mg/ml
Not quite as low as you wanted to go.
What if you added 10 ml of 0 mg/ml instead of 3.5 ml?
1080mg/40ml = 27 mg/ml
That's lower than you wanted to go, but getting closer.
What if you added 8 ml?
1080mg/ 38ml= 28.42 mg/ml
Pretty close!
You can keep trying this math with different volumes of 0 mg/ml juice/VG until you hit something close. This is what my math teachers used to refer to as 'plug and chug math'.
Method #2- use a formula to figure out the *exact* amount to use:
If you'd rather figure it out exactly with a formula this is the formula you'd use, and I'm not going to explain the derivation of the forumla here):
((36mg/ml*30ml) - (28mg/ml*30ml))/(28mg/ml -0mg/ml)=
(1080mg - 840mg)/28mg/ml=
240mg/28mg/ml= 8.57 ml
So, you'd add 8.57 ml of your 0mg/ml diluting juice to 30 ml of the 36 mg/ml juice.
Let's check our math... you still have 1080 mg of nicotine, but now it's in 38.57 mls total:
1080mg/38.57ml = 28.001 mg/ml