How long can it sit out?
CDC Human Milk Storage Guidelines, exactly. Pick where the milk is and when it was pumped — we'll tell you how long you've got.
Every storage window, in one place
No timer needed to get the gist — here's the full CDC reference table for how long expressed breast milk holds up in each spot, so you can check it at a glance whether or not you run the calculator above.
A few things that make these limits actually work in practice: store bottles or bags toward the back of the fridge or freezer, never the door, where temperature swings the least. Label everything with the pumping date so older milk gets used first. And once frozen milk has been thawed, it's a one-way trip — CDC guidance says use it within 24 hours and don't refreeze it. If milk is ever past its window, smell is your fastest check: a sour or soapy smell means it's time to toss it.
Reference: CDC Human Milk Storage Guidelines (cdc.gov/breastfeeding/recommendations/handling-breastmilk.html) — the same source behind the calculator and the honesty note below.
These are the CDC's published time limits. They're conservative on purpose — milk can sometimes last longer (especially in a cold fridge), but the CDC numbers are the ones every lactation consultant cites.
Smell + appearance are still your final test. Soured milk smells sharp and tangy — that's bacterial growth and it should go. Slight separation or yellowing is normal.
Source: CDC Human Milk Storage Guidelines (cdc.gov/breastfeeding/recommendations/handling-breastmilk.html).