U edited ur post.
200 ml of pre-mix Hangsen ....
ffs decant to something smaller & store the main bottle in the freezer

Learn to use an online calculator or install ejuicemeup

Oh- u wanted someone else to do all the calculations?
I cbf
If the need for final PG/VG ratio was in ur post, I prolly ignored it.

I should have said
"There are a heap of online calculators, and ejuicemeup- learn to use one".
and prolly
"200 ml of FT pre-mix Hangsen- what a waste of money unless u decant to something smaller & store the main bottle in the freezer "

My apologies.
Better late that never.

Did u understand that? ^

If the flavouring was PG based, it could drastically alter the final VG:PG ratio, depending on both the flavour concentration in the base, and the quantity added. So, these 100% VG eliquids might be nothing like that!

In the case of the 70:30 PG:VG mixture it shouldn't make much difference what the flavouring was in to start with, as the manufacturer would/should [some don't] simply adjust the quantities of PG/VG separately to get a final 70:30 ratio.


Flambo unnecessarily wrote:

Using a 'juice calculator' isn't 'doing your own maths'. Although they seem to give good results and are user friendly, they might not be programmed to deal with all mixing scenarios.

In any case it's always a good idea to ask here to get a second opinion, as it's easy to make errors when inputting values into these apps; most vapers here (with a few notorious exceptions) will have some useful input and advice, and you can get a consensus of the varying opinions.

If you really want to 'do your own maths', just use the standard equation (programmed into the 'juice calculators'), which you can use individually for any particular component, whether PG, VG, Nic or flavouring.

C₁V₁ + C₂V₂ = C₃V₃

and the rearranged versions:

C₃ = (C₁V₁ + C₂V₂) ÷ V₃

V₂ = (C₃V₃ - C₁V₁) ÷ C₂

Where C₁ & C₂ are concentrations of a particular component in the initial 2 portions of liquid of volumes V₁ & V₂, and V₃ is the final volume with concentration C₃.

In your example V₁, V₂, V₃, C₁, C₂ are all known, and the unknown is C₃: therefore use equation 2 (which many answerers did in their heads).

V₁ = V₂ = 100 mL
C₁ = 70 (mL PG/100 mL liquid)
C₂ = 0
V₃ = 200 mL

C₃ = (70 x 100 + 0 x 100) ÷ 200 = 35% PG
Therefore the remainder [65%] is VG

This result is good enough for vapers, but not totally accurate: for retail purposes one would need to take into account the quantity of nicotine & flavourings (which might be 2-5%) and flavour carrier, so the actual PG percentage might be slightly/very different.

The infamous Five Pawns results show that even so-called professional juice manufacturers aren't immune from mistakes, leading to gross errors in both nic concentrations and PG:VG ratios in their supposedly 50:50 pg:vg 6mg range.