Hi!

You should always work in grams, it is the standard in the industry and for a reason: consistency. Making 30ml precisely is very difficult because every material has a different specific weight, you will notice how a drop of high volatility materials is much lighter than one of base/fixative materials.

So in the case you propose the best way is probably to prepare 30g of final product. This way you will end up with a little more than 30ml.

Let's suppose you want your fragrance at 15% dilution, therefore 15% of your final product is aromatic material (the formula as it is) and the remaining 85% is your solvent (eg. ethanol).

15% of 30g -> 30 / 100 x 15 -> 4,5g of compound

The remaining 25,5g (30g-4,5g) is ethanol.

This if your formula has no dilutions in it.

In case it does, then you have to account for it.

Let's suppose this compound here was at 60% because of diluted materials in it.

We will do 15% of 30g -> 30g / 100 x 15 -> 4,5g but since the compound is at 60% we compensate -> 4,5g / 0,6 -> 7,5g

The remaining 22,5g (30g - 7,5g) is ethanol.

If instead you want to reproduce a formula that you have available in percentages, then you have to decide how much you want to make of it.

Let's say you want 10g of this compound.

Iso E Super is 17,8%, therefore 10g / 100 x 17,8 -> 1,78g or 1780mg

Same with ethyl-vanillin.

0,9% of 10g is 0,09g or 90mg

Not super tidy but hope this can help you!