Breast Milk Storage Duration Calculator
Freshly expressed breast milk keeps for different lengths of time depending on where it is stored. CDC guidance allows up to 4 hours at room temperature, up to 4 days in the refrigerator, and about 6 months (up to 12 acceptable) in the freezer. Select where the milk is, enter how many hours it has already been stored, and this calculator shows the CDC maximum duration and the time remaining before it should be used or discarded. The durations are editable so you can follow your own clinic's advice. These figures are for fresh milk, not thawed milk.
Storage duration formula
Room temperature max = 4 hours
Refrigerator max = 4 days = 96 hours
Freezer target = about 6 months (up to 12 acceptable)
Hours remaining = max storage hours - hours stored so far
Percent used = hours stored so far / max storage hours * 100
Selecting a location loads the CDC default maximum, which you can override. A negative remaining time means the storage window has been exceeded.
Breast milk storage context
- Fresh milk: up to 4 hours at room temperature per CDC guidance.
- Fresh milk: up to 4 days (96 hours) in the refrigerator.
- Fresh milk: about 6 months in the freezer for best quality, up to 12 acceptable.
- Thawed milk has stricter limits and should not be refrozen.
- This tool applies published durations only and is not medical advice.
Breast milk storage: frequently asked questions
How long can freshly expressed breast milk be stored?
The U.S. Centers for Disease Control and Prevention storage guidance for freshly expressed breast milk is up to 4 hours at room temperature (up to 77 degrees Fahrenheit), up to 4 days in the refrigerator (40 degrees Fahrenheit), and about 6 months (up to 12 months acceptable) in a freezer (0 degrees Fahrenheit or colder).
How does this calculator work?
You select where the milk is stored and enter how many hours it has already been there. The calculator shows the CDC maximum duration for that location and how much time remains before it should be used or discarded. The default durations follow CDC guidance and remain editable so you can apply your own clinic's advice.
Do these durations apply to thawed milk?
No. The figures here are for freshly expressed milk. Once previously frozen milk has thawed, the CDC advises using it within 24 hours in the refrigerator and within 2 hours at room temperature, and not refreezing it. Use the appropriate guidance for thawed milk rather than these fresh-milk figures.
Why is the freezer figure given as a range?
The CDC says frozen breast milk is best used within about 6 months but is acceptable up to 12 months. Storing longer is not unsafe, but quality declines over time as some fats break down, which is why a shorter target is recommended for best quality.
Is this calculator medical advice?
No. It applies published CDC storage durations to a simple time calculation for general information. Premature or hospitalized infants may need stricter handling. Always follow the guidance of your pediatric or lactation care team.
Official sources
- U.S. Centers for Disease Control and Prevention: Breastfeeding and human milk storage.
- U.S. National Library of Medicine, MedlinePlus: storing breast milk.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.