Breast milk expiration calculator (CDC, ABM & NHS rules)
Enter when the milk was expressed, where it's been since, and which guideline you follow. You get an estimated limit date and time, plus the exact table row and source that produced it — so you can see the reasoning, not just the answer. Switch to "pooled" if you're combining several pumping sessions into one bag.
Short answer
CDC figures; switch to ABM or NHS in the calculator · not medical advice
Expiration calculator
Portions you want to combine
The table row behind it
An estimate from the guideline you selected — not medical advice. Actual fridge and freezer temperatures, door openings and handling all matter. When in doubt about a bag, ask your pediatrician or an IBCLC.
How does the calculator work?
It's arithmetic on a published table. Each guideline gives one limit per storage condition; the calculator adds that limit to your expression time. Thawed milk is the one condition that starts from a different moment — from fully thawed, not from expression — so for that row you enter when the bag finished thawing. Where a guideline publishes no figure for a condition, the calculator says so instead of borrowing a number from somewhere else.
Why do the CDC, ABM and NHS rules differ?
They mostly don't. The core figures — about 4 hours at room temperature, 4 days in the fridge, 6 months in the freezer — line up across the CDC and the ABM. The differences are in the edges: how much extra the ABM allows "under very clean conditions", how the NHS frames the fridge by temperature rather than by a single number, and what each one simply doesn't publish.
| Condition | CDC | ABM | NHS |
|---|---|---|---|
| Room temperature | Up to 4 hours | 4 hours optimal; 6–8 hours acceptable under very clean conditions | The NHS page publishes no room-temperature figure |
| Refrigerator | Up to 4 days | 4 days optimal; 5–8 days under very clean conditions | Up to 8 days — within 3 days if the fridge runs 5–10 °C or you don't know its temperature |
| Ice compartment (no separate door) | The CDC publishes no figure for this | The ABM publishes no figure for this | 2 weeks |
| Freezer | About 6 months is best; up to 12 months is acceptable | 6 months optimal; 12 months acceptable | Up to 6 months |
| Cooler with ice packs | Up to 24 hours | 24 hours | Up to 24 hours |
| Thawed, in the fridge | Use within 24 hours from fully thawed | 24 hours from thawed (the protocol counts a thawed window of 24 hours) | "Use it straight away" — the NHS publishes no hour figure |
| Leftover from a feeding | Use within 2 hours, then discard | Discard within 1–2 hours after the feeding ends | Use within 1 hour, then throw away what is left |
| Refreezing | Never refreeze after it has thawed | The ABM makes no recommendation on refreezing thawed milk | Do not re-freeze milk that has been defrosted |
- CDC — the table most US pediatricians quote. One number per row, no "acceptable under ideal conditions" tiers except the freezer's 6-vs-12 months.
- ABM Protocol #8 — a clinical protocol for full-term infants at home. Same optimal figures as the CDC, with explicit outer bounds for very clean handling (6–8 hours at room temperature, 5–8 days in the fridge). It makes no recommendation at all about refreezing.
- NHS — written for UK parents. Up to 8 days at the back of a fridge at 4 °C or lower (3 days if the fridge runs warmer or you don't know), 2 weeks in a fridge's ice compartment, 6 months in a freezer. It publishes no room-temperature figure and no hours for defrosted milk — just "use it straight away".
None of them is "right" and the others "wrong"; they're written for different readers with different levels of caution baked in. The useful move is to pick the one your pediatrician or health service follows and apply it consistently — which is why the calculator lets you pick, and why it names the guideline on every result.
What about a deep freezer, or a cooler on the way to daycare?
Deep freezer: Neither the CDC nor the ABM publishes a separate figure for a deep freezer or chest freezer — the standard freezer row is the only published estimate, so that is what this calculator uses. It's a common belief that −20 °C buys extra months; no source we cite publishes that.
Cooler with frozen ice packs: up to 24 hours per the CDC (for travel), 24 hours per the ABM, and up to 24 hours per the NHS for milk already cooled in the fridge. All three agree on the number, and all three assume the ice packs are actually frozen when you leave.
Can I combine milk from different pumping sessions?
Don't add freshly expressed warm milk to milk that is already cold or frozen — cool the new milk in the fridge first, then combine (ABM Protocol #8). The combined portion keeps the oldest portion's date. That's what the calculator's pooled mode does: enter each portion's time, and the oldest one sets the clock for the whole bag. Amounts are optional — they're only added up so you know what you're freezing.
What does "expires" mean here?
An estimate. The guideline tables assume a fridge that is actually at 40 °F (4 °C) or colder, a freezer that stays at 0 °F (−18 °C), and milk that was handled cleanly. Your appliances and your day are your own — the calculator has no thermometer, and neither does an app. When a specific bag is a judgment call, ask your pediatrician or an IBCLC. Every date on this page is an estimate from published guidance, never medical advice.
Milkloft runs this calculator on every bag you log, automatically: the expression time, the location it's in, and the guideline you chose in Settings (CDC by default — editable, with the source shown next to each number) produce an estimated date that updates when the bag moves from freezer to fridge to bottle. One-time purchase, no account.
Frequently asked questions
How do I calculate when breast milk expires?
Take the date and time it was expressed, add the limit for where it is stored, and you have the estimated limit. Per the CDC: up to 4 hours at room temperature, up to 4 days in the fridge, about 6 months in the freezer (up to 12 acceptable), and 24 hours in the fridge once thawed. The calculator on this page does the arithmetic and shows the row it used.
Which guideline should I use: CDC, ABM or NHS?
Whichever your pediatrician, lactation consultant or country's health service follows — then stick with it. The three share the core numbers (4 hours, 4 days, 6 months); they differ in the outer bounds and in what they don't publish. The CDC is the most widely cited in the US and is Milkloft's default.
Does the freezer limit count from the day I pumped or the day I froze it?
The guideline tables are written from the moment of expression, and that is the cautious way to count: a bag that spent two days in the fridge before freezing is two days older than a bag frozen straight away. Milkloft counts the freezer window from the expression date for that reason.
Does a deep freezer make breast milk last longer?
No published figure says so. Neither the CDC nor the ABM publishes a separate limit for a chest or deep freezer at −20 °C — the standard freezer row (about 6 months best, up to 12 acceptable per the CDC) is the only figure, and that is what this calculator uses.
If I mix milk from two pumping sessions, which date do I use?
The oldest one. The combined portion takes the clock of its oldest milk. And per ABM Protocol #8, don't add warm, freshly expressed milk to milk that is already cold or frozen — cool the new milk in the fridge first, then combine.