Dilution calculator

From neat oil to a working solution. It tells you how many milligrams to weigh, and when the amount is too small to weigh directly — at which point you have to go through a stock solution.

Every figure is a percentage by weight. You weigh, so the calculator works in grams — not in ml, not in drops. A drop of essential oil is anything from 0.03 to 0.07 ml depending on the dropper; the ml and drop figures below are only there to help you picture it, not to measure with.

What you want to make

Target concentration % Target mass g Solvent Essential-oil density g/ml

Dilution ladder

From neat down to the target concentration, each step a tenfold dilution. Each row is a separate vessel of the same target mass. Where a step can be weighed directly, weigh it directly; where it is too small, take solution from the step above and add solvent — the “solvent to add” column already subtracts the solvent contained in the amount you take.

Concentration	Take from step above	Solvent to add	Method

Why weigh rather than count drops

How much a drop holds depends on the dropper, on the substance and on the room temperature. Two people making the same formula by drops will end up with two different bottles, and nobody will know why. Weighing is repeatable — which is why every formula in the trade is written in parts per thousand by weight, not in drops.

Density is used only to convert to ml and drops so you can picture the amounts — it does not enter the main calculation. Real essential oils range from 0.84 to 0.98 g/ml depending on the type; enter your own lot’s figure if you have it.