Breast Milk Storage Calculator
Find the use-by date and time remaining for pumped breast milk based on CDC storage guidelines.
Storage Tips
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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This calculator applies the latest CDC breast milk storage guidelines to tell you exactly when your pumped milk expires. Here is how to use it:
- Enter the date and time you pumped. Use the date and time picker to enter when the milk was expressed. The calculator uses this as the starting point.
- Select your storage location. Choose from room temperature, insulated cooler, refrigerator, freezer compartment, separate deep freezer, or previously frozen and thawed milk. Each has a different safe storage window.
- Read the result. The calculator shows the exact use-by date and time, how much time is remaining, and the maximum storage duration for that method.
- Follow the safety tips. Scroll down to see storage tips specific to your chosen method, including how to check temperature and how to properly label containers.
Results update instantly. Use Copy to paste the use-by time into a note, or Share to send the link to a caregiver.
About Breast Milk Storage Guidelines
The CDC and American Academy of Pediatrics (AAP) publish evidence-based guidelines for how long pumped breast milk remains safe and nutritious. The general rule is called the "Rule of 4s": room temperature up to 4 hours, refrigerator up to 4 days. Frozen milk in a separate deep freezer can last 6 months at best quality and up to 12 months acceptably. These guidelines apply to freshly expressed milk from a healthy mother for a healthy, full-term baby. Premature infants or babies in the NICU may have stricter requirements - always consult your care team.
Once frozen milk is thawed in the refrigerator, it must be used within 24 hours and must never be refrozen. Once milk is warmed, any unused portion should be discarded within 2 hours. All calculations run entirely in your browser with no data stored or transmitted.
Frequently Asked Questions
How long does breast milk last in the refrigerator?
According to CDC guidelines, freshly expressed breast milk can be safely stored in the refrigerator at 40°F (4°C) or colder for up to 4 days. Store milk at the back of the refrigerator where the temperature is most consistent, not in the door. Label each container with the date and time pumped, and always use the oldest milk first.
Can you refreeze thawed breast milk?
No. Once breast milk has been thawed, it must not be refrozen. Thawed milk stored in the refrigerator must be used within 24 hours. Once milk has been warmed, any unused portion should be discarded within 2 hours. Refreezing causes fat separation and degrades the protective antibodies in the milk.
How long does breast milk last in a freezer?
In a separate deep freezer maintained at 0°F (-18°C) or colder, breast milk is best used within 6 months but remains acceptable for up to 12 months. In the freezer compartment built into a refrigerator (which is less cold), milk should be used within 2 weeks. Always freeze in small amounts (2-4 oz) to minimize waste after thawing.
How long can breast milk sit out at room temperature?
Freshly expressed breast milk can remain at room temperature (up to 77°F/25°C) for up to 4 hours. In a cooler or warmer room, or if the milk has been previously refrigerated or thawed, this window may be shorter. If in doubt, refrigerate or discard the milk. The "smell test" is not reliable for determining breast milk safety.