Foundation expires, and the date that matters is the date you open it, not the date you buy it. The little open-jar symbol with a number like “12M” is the period-after-opening (PAO): how many months the product stays safe and effective once you first break the seal.
What the PAO number means
“12M” means twelve months after opening; “6M” means six. Liquid foundation typically carries a 6-12M rating and serums 3-6M, in line with the reference ranges we track. After that window, texture, color, and active ingredients can degrade even if the bottle is not empty.
When expiry costs you money
If a bottle would take longer to use up than its PAO allows, you are paying for product you will throw away. That is most common with large sizes used a few times a week, or backup shades you rotate slowly. The smaller bottle is often cheaper in practice once you count the waste. To turn your bottle into an applications count, see how many pumps or drops are in a 30 ml bottle.
Typical PAO windows at a glance
Ratings vary by brand, but these are the common ranges to expect once a product is opened:
- Liquid foundation: usually 6-12M.
- Serums and treatments: often 3-6M, since actives degrade faster.
- Powder foundation and blush: generally longer, frequently 12-24M.
- Mascara and liquid eye products: the shortest, commonly 3-6M.
Storing bottles cool, capped, and out of direct sun helps them reach the full window rather than turning early.
Check yours before you buy bigger
The longevity calculator compares how long your bottle lasts on usage against its PAO date and flags whichever runs out first, including an estimate of the dollars you would waste if it expires before you finish it.