Storage windows
This calculator uses the storage times recommended by the CDC breast milk handling guide and ABM Clinical Protocol #8: up to 4 hours at room temperature (≤25°C), up to 4 days in the refrigerator (≤4°C), 6 months recommended (12 acceptable) in the freezer (≤-18°C), up to 24 hours in the fridge after thawing, and used within 2 hours if thawed at room temperature.
What to watch out for
The guidelines below assume a healthy, full-term baby. Premature or immunocompromised babies and hospital settings require stricter limits. Also keep these in mind.
- Don't refreeze thawed milk. Bacteria can grow during thawing. Use thawed milk within 24 hours.
- Milk the baby has fed from must be used within 2 hours. Saliva introduces microbes that shorten the safe window.
- Store at the back of the freezer, not the door. Frequent door openings cause temperature swings that degrade quality.
- Use BPA-free breast milk storage bags or food-grade containers. Ordinary plastic bags are not suitable.
Frequently asked questions
Can I refreeze thawed milk?
No. Both the CDC and ABM advise against refreezing once thawed: bacteria can begin to grow, and nutritional and immune components degrade. Discard any thawed milk not used within 24 hours.
Can I put milk back in the fridge after it sat at room temperature?
If the baby has not fed from it and it sat at room temperature for under 2 hours, yes — but count the total storage time from when it was first expressed. Milk the baby has fed from should not go back in the fridge.
My frozen milk changed color — is it spoiled?
Breast milk can naturally shift to yellow, bluish, or pink tones depending on diet, storage time, and fat separation. A soapy smell is a normal lipase reaction (safe but the baby may refuse it); a sour or rancid smell means discard.