What this calculator does
Freshly expressed breast milk is safe for a limited time depending on where it is stored. This calculator takes the date and time you pumped and the storage location, then adds the recommended limit to tell you exactly when the milk should be used or discarded. The guidelines used here follow common public-health recommendations (CDC) for healthy full-term infants.
Storage limits used
The calculator applies these widely cited limits to freshly pumped milk:
Room temperature (up to 25°C / 77°F): 4 hours.
Refrigerator (4°C / 40°F or colder): 4 days.
Freezer (-18°C / 0°F or colder): about 6 months for best quality (up to 12 months acceptable).
How to use it
Pick the storage location, enter the date you expressed the milk, and the hour and minute. The result shows the latest date and time the milk should be used. Always store milk in clean, sealed containers and label each one with the pump time.
Worked example
You pump at 8:00 AM on 2024-01-01 and refrigerate it. The fridge limit is 4 days, so the safe-until time is $$\text{Safe Until} = \text{2024-01-01}\;08\!:\!00 + 4\;\text{days} = \text{2024-01-05}\;08\!:\!00$$ If instead you left it at room temperature, you would add 4 hours, giving $$\text{Safe Until} = \text{2024-01-01}\;08\!:\!00 + 4\;\text{hours} = \text{2024-01-01}\;12\!:\!00$$
Breast Milk Storage Limits by Type
The Centers for Disease Control and Prevention (CDC) publishes guidelines for how long human milk can safely be stored, depending on the milk's condition and where it is kept. The limits differ for freshly expressed milk, milk that has been thawed after freezing, and milk left over after a feeding. The table below summarizes the recommended maximums for healthy, full-term infants at home.
| Milk type | Room temperature (up to ~77°F / 25°C) | Refrigerator (~40°F / 4°C) | Freezer (~0°F / -18°C) |
|---|---|---|---|
| Freshly expressed / pumped | Up to 4 hours | Up to 4 days | About 6 months is best; up to 12 months acceptable |
| Thawed (previously frozen) | 1–2 hours | Up to 24 hours | Never refreeze after thawing |
| Leftover from a feeding (baby drank from the bottle) | Use within 2 hours after the baby finishes | Use within 2 hours after the baby finishes | Do not store |
Notes: Always store milk in clean, sealed containers and label each with the date it was expressed. Use the oldest milk first. The 4-day refrigerator limit assumes milk is kept toward the back of the fridge where the temperature is most stable, not in the door. Cooled or frozen milk that is being transported should be kept in an insulated cooler with ice packs.
FAQ
Can I refreeze thawed milk? No. Once thawed, use refrigerated thawed milk within 24 hours and never refreeze it.
What about previously frozen milk? These limits apply to freshly expressed milk. Thawed milk has shorter limits.
Is the 6-month freezer figure exact? It is a best-quality guideline; milk may be safe up to 12 months frozen, but quality declines. This tool uses 6 months.
