Free calculator
Shelf life calculator
How long a material keeps is decided by its chemistry, not by the note it plays. Choose what it is mostly made of and how you keep it, and this gives the day to smell it again before trusting it.
The sum, in words
Find the class of molecule the material is mostly made of, and take its figure for cool storage. For a bottle kept at room temperature, halve it. Add that many months to the day the bottle was first opened, and that is the day to smell it again before trusting it.
Lavender is alcohol-rich, which is 36 months cool and 18 at room temperature. A bottle opened on 31 January 2026 and kept on a shelf reaches its date 18 months later, on 31 July 2027.
When the day does not exist in the month you land on, the date is that month's last day. The same bottle opened on 31 August 2026 lands in February 2028, which has 29 days, so its date is 29 February 2028.
The figures, by class
| Mostly made of | Kept cool | At room temperature |
|---|---|---|
| Citrus peel, conifers, olibanum, pepper, galbanum | 24 months | 12 months |
| Lemongrass, litsea, bitter almond, the C-aldehydes | 24 months | 12 months |
| Eucalyptus, rosemary, laurel, cardamom | 36 months | 18 months |
| Lavender, geranium, linalool, phenylethyl alcohol | 36 months | 18 months |
| Clove, cinnamon leaf, anethole, vanillin | 48 months | 24 months |
| Salicylates, acetates, lactones, Hedione | 48 months | 24 months |
| Ionones, damascones, jasmones, musks | 60 months | 30 months |
| Patchouli, vetiver, sandalwood, cedarwood | 96 months | 48 months |
| Absolutes, concretes, resinoids, balsams | 60 months | 30 months |
| A fatty carrier oil | 24 months | 12 months |
| Solvents: DPG, IPM, TEC, benzyl benzoate, ethanol | 120 months | 60 months |
The sesquiterpene woods at the long end tend to improve with age rather than decline. A fatty carrier oil goes rancid rather than losing its terpenes, which is a different change with its own test. The solvent figure is not an oxidation figure at all: it is a housekeeping interval, and a solvent that old should still be smelled before it carries a dilution.
A date to check, not a date to throw away
Reaching the date does not make a material unusable, and not reaching it does not make a material fine. It is the day the published guidance says to stop assuming. Smell it, look at it, and compare it with a fresh sample if you have one.
The reason it matters is safety as well as quality. Oxidized terpenes are more sensitizing than fresh ones, so a material that smells off, has thickened or has changed color should not go into a product whatever this date says. If the supplier gives a date of their own for the lot, go by whichever of the two comes first.
The clock starts when the bottle is opened
Not when it arrived. A sealed bottle has had very little air, and each opening lets more in. Write the opening date on the bottle the first time you open it, because it is the date this depends on and the one nobody remembers a year later.
What this calculator does not do
It does not give a date for a material whose chemistry you do not know, because a guessed class gives a guessed date. Nor is this the period after opening printed on a finished product. That is a statement about the product in a customer's hands, which is a different question with its own evidence behind it.