hello little human

Breast milk storage calculator

Was that bottle from 2pm, or yesterday? Let's not guess. Enter when you pumped and where the milk is. You get the time to use it by, from the CDC's storage guidelines.

The milk is
Where is it?

Breast milk storage at a glance

WhereFreshly pumpedThawed
CountertopUp to 4 hours1 to 2 hours
RefrigeratorUp to 4 daysUp to 1 day (24 hours)
FreezerWithin 6 months is best. Up to 12 months is acceptable.Never refreeze thawed breast milk

Leftovers: Use within 2 hours after your baby finishes feeding. After that, throw it away.

Traveling: In an insulated cooler bag with frozen ice packs, breast milk can be kept for up to 24 hours when you're traveling. When you arrive, use it, refrigerate it or freeze it right away.

  • Label each container with the date you pumped. Use the oldest milk first.
  • Store milk at the back of the fridge or freezer, not in the door.
  • Freeze in small amounts, 2 to 4 ounces, to waste less. Leave about an inch at the top: milk expands as it freezes.
  • If you won't use fresh milk within 4 days, freeze it right away.
  • Thaw in the fridge overnight, in a container of lukewarm water, or under lukewarm running water. Never in the microwave.
  • Milk thawed in the fridge: count the 24 hours from when it's fully thawed, not from when it left the freezer.
  • These times are for healthy, full-term babies. For a baby born early or sick, check with your health care provider.

Source: CDC, "Breast Milk Storage and Preparation." hellolittlehuman.com

The short version

CDC says freshly pumped breast milk keeps for up to 4 hours on the counter (77°F or colder), up to 4 days in the fridge, and up to 12 months in the freezer, though within 6 months is best. Milk thawed in the fridge keeps for up to 24 hours, counted from when it’s fully thawed. Once it’s at room temperature or warmed, use it within 2 hours. Never refreeze thawed milk. Leftovers from a feed are good for 2 hours after your baby finishes.

AAP’s own chart is a little more cautious about the freezer: up to 9 months in a standard freezer at 0°F, and up to 12 months only in a deep freezer at -4°F or colder.

Label everything. In the middle of the night, every bag of milk looks the same.

Storing it well

  • Use breast milk storage bags, or clean, food-grade glass or plastic containers with tight lids. Don’t use disposable bottle liners or plastic bags that aren’t made for breast milk.
  • Label each one with the date you pumped, and use the oldest first.
  • Keep it at the back of the fridge or freezer, not in the door, where the temperature changes more.
  • Freeze small amounts, 2 to 4 ounces, so less goes to waste. Leave about an inch at the top, because milk expands as it freezes.
  • If you won’t use fresh milk within 4 days, freeze it right away.
  • Traveling? An insulated cooler bag with frozen ice packs keeps milk for up to 24 hours. When you arrive, use it, refrigerate it or freeze it right away.

Thawing and warming

Thaw milk in the fridge overnight, in a container of lukewarm water, or under lukewarm running water. Never thaw or heat it in the microwave: it creates hot spots that can burn your baby’s mouth. Milk doesn’t need to be warmed. If you warm it, test a few drops on your wrist: it should feel warm, not hot. Swirl the milk to mix the fat back in.

When in doubt

If you’re not sure how long milk has been out, throw it out. These times are for healthy, full-term babies. If your baby was born early, is sick or is in the hospital, the guidance may be different: follow your care team’s advice.

Sources

  1. CDC, “Breast Milk Storage and Preparation” (updated 14 Aug 2026), and its printable sheet, “Storage and Preparation of Breast Milk.” cdc.gov
  2. American Academy of Pediatrics, “Tips for Freezing & Refrigerating Breast Milk.” healthychildren.org