# Breast Milk Storage Calculator

> Freshly pumped breast milk keeps up to 4 hours at room temperature, up to 4 days in the fridge, and about 6 months in the freezer (up to 12 months is acceptable), according to the CDC. Enter when you pumped, thawed or warmed it to see exactly when to use it by.

- Interactive calculator: https://www.leoella.com/tools/breast-milk-storage-calculator
- Plain-text version: https://www.leoella.com/tools/breast-milk-storage-calculator.md
- Category: Baby & Toddler
- Publisher: Leo&Ella (https://www.leoella.com)
- Last reviewed: October 19, 2026

## How it works

The calculator adds the CDC's storage limit for the milk to the date and time entered, which default to now. Freshly pumped milk is counted from when it was pumped: up to 4 hours at room temperature (77°F or colder), 24 hours in an insulated cooler with frozen ice packs, 4 days in the refrigerator, or about 6 months (best) to 12 months (acceptable) in the freezer. Milk thawed in the refrigerator gets 24 hours, counted from when it came out of the freezer, which is earlier than when it finished thawing and so errs on the safe side; milk that has been warmed or brought to room temperature, and milk left over from a feed, gets 2 hours. It shows the use-by time and how long is left, and reminds parents never to refreeze thawed milk.

## Key facts

- The CDC says freshly pumped breast milk can be kept at room temperature (77°F or colder) for up to 4 hours, in an insulated cooler with frozen ice packs for up to 24 hours when traveling, and in the refrigerator for up to 4 days. [1]
- The CDC says frozen breast milk is best used within about 6 months, and up to 12 months in the freezer is acceptable. [1]
- According to the CDC, breast milk thawed in the refrigerator should be used within 24 hours, milk brought to room temperature or warmed should be used within 2 hours, and breast milk should never be refrozen after it has thawed. [1]
- The CDC says breast milk left over from a feeding should be used within 2 hours after the baby finishes, then thrown away. [1]
- The AAP recommends storing breast milk at the back of a refrigerator at 39°F or colder, and gives up to 9 months in a freezer at 0°F or colder and up to 12 months in a deep freezer at −4°F or colder. [2]
- The AAP's easy rule for breast milk is the rule of 4s: 4 hours at room temperature and 4 days in the refrigerator. It says not to microwave breast milk, because of the risk of scalding the baby. [2]

## Reference data

### How long breast milk keeps (CDC)

Room temperature means 77°F or colder. Freezer dates are calendar months from the day the milk was frozen.

| Milk | Keeps for | Counted from | Note |
| --- | --- | --- | --- |
| Freshly pumped, room temperature | Up to 4 hours | When it was pumped | – |
| Freshly pumped, cooler with ice packs | Up to 24 hours | When it was pumped | Use it, refrigerate it or freeze it when you arrive. |
| Freshly pumped, refrigerator | Up to 4 days | When it was pumped | – |
| Freshly pumped, freezer | About 6 months is best; up to 12 months is acceptable | When it was pumped | – |
| Thawed in the fridge | Up to 24 hours | When it came out of the freezer | Never refreeze breast milk after it has thawed. Once it's at room temperature or warmed, use it within 2 hours. |
| Warmed or at room temp | Up to 2 hours | When it was warmed or reached room temperature | Never refreeze breast milk after it has thawed. |
| Left over from a feed | Up to 2 hours | When the baby finished feeding | – |

### Worked examples

| Situation | Starting | Use by |
| --- | --- | --- |
| Pumped and left at room temperature | Monday, March 2, 2026 at 9:00 AM | Monday, March 2, 2026 at 1:00 PM |
| Pumped into a cooler with ice packs for a drive | Saturday, June 6, 2026 at 7:00 AM | Sunday, June 7, 2026 at 7:00 AM |
| Pumped and put in the refrigerator | Monday, March 2, 2026 at 9:00 AM | Friday, March 6, 2026 at 9:00 AM |
| Pumped and frozen | Thursday, January 15, 2026 at 9:00 AM | Best by Wednesday, July 15, 2026; use by Friday, January 15, 2027 |
| Taken out of the freezer to thaw in the refrigerator | Tuesday, March 3, 2026 at 8:00 PM | Wednesday, March 4, 2026 at 8:00 PM |
| Warmed for a feed | Wednesday, March 4, 2026 at 6:00 AM | Wednesday, March 4, 2026 at 8:00 AM |
| Left in the bottle after a feed | Wednesday, March 4, 2026 at 6:30 PM | Wednesday, March 4, 2026 at 8:30 PM |

## Frequently asked questions

### How long is breast milk good for at room temperature?

Freshly pumped breast milk can stay at room temperature (77°F or colder) for up to 4 hours, according to the CDC. It's best to refrigerate or chill it as soon as you can.

### How long does breast milk last in the fridge?

Up to 4 days for freshly pumped milk, according to both the CDC and the AAP. The AAP recommends storing it at the back of the refrigerator, at 39°F or colder, where the temperature changes least.

### How long can breast milk be frozen?

The CDC says about 6 months is best and up to 12 months is acceptable. The AAP gives up to 9 months in a freezer at 0°F or colder and up to 12 months in a deep freezer at −4°F or colder.

### How long is thawed breast milk good for?

Milk thawed in the refrigerator should be used within 24 hours. Once it has been brought to room temperature or warmed, use it within 2 hours. Never refreeze breast milk after it has thawed.

### Can I save breast milk my baby didn't finish?

Only for a short time: use milk left over from a feeding within 2 hours after your baby finishes, then throw it away. Storing milk in small amounts, the AAP suggests 2 to 4 ounces, helps avoid waste.

### How long does breast milk last in a cooler?

Up to 24 hours in an insulated cooler with frozen ice packs when you're traveling, according to the CDC. When you arrive, use it, refrigerate it or freeze it.

## Sources

1. [CDC: Breast Milk Storage and Preparation](https://www.cdc.gov/breastfeeding/breast-milk-preparation-and-storage/handling-breastmilk.html)
2. [AAP (HealthyChildren.org): Storing and Preparing Expressed Breast Milk](https://www.healthychildren.org/English/ages-stages/baby/breastfeeding/Pages/Storing-and-Preparing-Expressed-Breast-Milk.aspx)

## About this page

This is general information for parents, not medical advice; a doctor, midwife or pediatrician who knows the family should guide individual decisions. The calculator runs in the visitor's browser and stores nothing they enter. When quoting this page, cite "Breast Milk Storage Calculator, Leo&Ella" and link https://www.leoella.com/tools/breast-milk-storage-calculator.