How much expressed breast milk should I leave for my baby?

The simplest guide is about 1 to 1.25 oz (30–37 ml) of milk for every hour you'll be away. So an 8-hour day works out to roughly 8–10 oz (240–300 ml). If you'd rather think about it per feed, take the ~25 oz (750 ml) a breastfed baby averages over a full day and divide by the number of feeds — usually 3–4 oz (90–120 ml) a bottle. Leaving a little extra in a small spare bottle covers a hungry day.

How much milk should I send to daycare per bottle?

Send small bottles of about 2–4 oz (60–120 ml) each rather than a few large ones. Milk left in a bottle after a feed should be used within roughly 2 hours and then thrown out, so smaller portions mean far less waste. Total the hours your baby is in care, plan on ~1–1.25 oz per hour, and split that into 2–4 oz bottles, plus one spare.

Does the amount of breast milk go up as my baby gets bigger?

Surprisingly, no — not the way formula does. Between about 1 and 6 months, a breastfed baby's daily intake stays roughly flat at 25 oz (750 ml) even as they double in weight. Breast milk changes in fat and calorie content over time to match your baby's growth, so they don't need to drink more. This is the biggest difference from formula, which is dosed by weight and keeps climbing.

Why not just use a formula calculator?

Because a formula calculator sizes bottles from your baby's weight — about 150 ml per kilogram per day — and that math doesn't apply to expressed breast milk, whose daily total stays flat from 1 to 6 months. Using a weight-based formula number for pumped milk usually overestimates how much a growing baby needs. If your baby is formula-fed or combination-fed, use the formula calculator for the formula portion and this tool for the breast-milk portion.

My baby takes much more (or less) than 25 oz a day. Is that normal?

Very likely yes. The 25 oz figure is an average; the normal range for exclusively breastfed babies runs from about 19 to 30 oz (570–900 ml) a day. Some babies take smaller, more frequent feeds and others larger, less frequent ones, and it evens out. As long as your baby is growing well and making plenty of wet diapers, the exact number matters less than the trend. Raise any worries about intake or supply with your pediatrician or a lactation consultant.

How much milk do I need to leave for an 8-hour work day?

For an 8-hour day, plan on roughly 8 to 10 oz (240–300 ml) total, using the ~1–1.25 oz per hour rule — then split it into three or four small bottles of 2–4 oz so nothing is wasted. Pump around the times your baby would normally feed to keep your supply matched to what's going out, and refrigerate or freeze what you express that day for the next one.

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Breast Milk Calculator: How Much Expressed Milk to Leave

Pumping and leaving bottles? Work out how much expressed breast milk to leave — by the hours you're away or per feed — in millilitres or ounces.

Units

Hours you'll be away

8hours

Leave

8–10 oz

for 8 hours away

Bottles

of about 3.5 oz

Based on ~1–1.25 oz of milk per hour away — the low end suits younger or lighter eaters, the high end older or hungrier ones. Splitting the milk into small bottles means less is thrown out if your baby doesn't finish one.

Typical reference ranges, not medical advice — every baby is different. Follow your baby's hunger and fullness cues, and ask your pediatrician or a lactation consultant about anything that worries you.

If you're pumping and leaving bottles — for daycare, a work day, or a night out — the question is always the same: how much expressed breast milk is enough? This tool uses the two methods lactation experts actually use: the milk-per-hour-away rule, and the flat daily average split across feeds.

Looking for infant formula amounts instead? Breast milk and formula work differently, so use the baby formula calculator — its weight-based numbers don't apply to expressed breast milk.

Here's the single most useful thing to know: expressed breast milk intake does not keep rising as your baby grows. Between 1 and 6 months, a breastfed baby's daily total stays remarkably steady at around 25 oz (750 ml) — so a bottle for a 3-month-old and a 6-month-old is about the same size. Formula, by contrast, is dosed by weight and climbs steadily. Everything below explains why, and how to size a bottle from it.

Why Expressed Milk Doesn't Scale With Weight

A formula calculator multiplies your baby's weight by roughly 150 ml per kilogram, so the daily amount keeps rising as the baby gets heavier. It's tempting to assume breast milk works the same way. It doesn't.

Research on exclusively breastfed babies found that milk intake climbs quickly in the first weeks, then levels off around one month and stays almost flat — an average of about 25 oz (750 ml) a day — all the way to six months, even as the baby doubles in weight. Breast milk changes in composition and fat content over time to keep pace with growth, so the baby doesn't need to drink more of it. A bigger baby isn't a hungrier baby here.

This is why a per-kilogram formula gives the wrong answer for expressed milk, and why it's worth reaching for the right tool. If your baby is formula-fed or combination-fed, the formula calculator handles the weight-based side.

Expressed breast milk

Flat at ~25 oz (750 ml) a day from 1 to 6 months, regardless of weight. Sized by hours away or by splitting the daily total across feeds — usually 3–4 oz (90–120 ml) a bottle.

Infant formula

Dosed by body weight — about 150 ml per kg per day — so the daily total and bottle size both climb as the baby grows, up to around 1 litre a day.

How Much to Send to Daycare Per Bottle

For childcare, the goal is bottles that match how your baby actually eats without wasting hard-earned milk. A few simple rules keep it manageable:

Send small bottles — about 2–4 oz (60–120 ml) each. A caregiver can always warm another one, but milk left in a bottle after a feed should be used within about 2 hours and then discarded, so smaller portions waste far less.
Label every bottle with your baby's name and the date it was pumped, and send it chilled or frozen with a note on how many ounces your baby usually takes per feed.
Plan on roughly 1–1.25 oz per hour away, then round up by a bottle. An extra small bottle in the bag covers a growth-spurt day without committing you to oversized portions every day.
Ask the caregiver to offer the freshest milk first and to pace-feed slowly — a slow-flow nipple and breaks help a breastfed baby take a bottle without overeating, which keeps daily totals realistic.

Rule of thumb: total the hours away, plan ~1–1.25 oz per hour, and split it into 2–4 oz bottles. It's better to send several small bottles than a couple of big ones you'll end up pouring away.

Expressed Milk Storage: Quick Reference

Once you've pumped, storing it well protects both the milk and your effort. These are the general CDC ranges for healthy, full-term babies at home — a signpost, not a substitute for the full guidance, which is linked below.

Where	Freshly expressed milk keeps for
Countertop (room temperature)	Up to about 4 hours
Refrigerator	Up to about 4 days
Freezer	About 6 months (best), up to 12
Thawed, in the fridge	Use within about 1 day — never refreeze

General ranges for home use, not medical advice — premature or hospitalised babies follow stricter rules. Milk left over after a feed should be used within about 2 hours. For the full, current guidance, see the CDC and AAP links below.

Sources & Limitations

The intake figures here follow published lactation research and guidance; the storage ranges follow current CDC advice. They're typical reference ranges to help you plan a pump stash — every baby varies, and a healthy total can sit anywhere from roughly 19 to 30 oz a day.

General reference ranges, not medical advice — every baby is different. This page doesn't cover diagnosis, treatment, or feeding difficulties; for concerns about your milk supply, your baby's intake, or weight gain, talk to your pediatrician, midwife, or an IBCLC lactation consultant.

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Doudou logs every nursing session, bottle, and pumping session in a couple of taps — so you can see how much your baby is taking and how much milk you have stashed, synced between both parents.

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Frequently Asked Questions

How much expressed breast milk should I leave for my baby?: The simplest guide is about 1 to 1.25 oz (30–37 ml) of milk for every hour you'll be away. So an 8-hour day works out to roughly 8–10 oz (240–300 ml). If you'd rather think about it per feed, take the ~25 oz (750 ml) a breastfed baby averages over a full day and divide by the number of feeds — usually 3–4 oz (90–120 ml) a bottle. Leaving a little extra in a small spare bottle covers a hungry day.
How much milk should I send to daycare per bottle?: Send small bottles of about 2–4 oz (60–120 ml) each rather than a few large ones. Milk left in a bottle after a feed should be used within roughly 2 hours and then thrown out, so smaller portions mean far less waste. Total the hours your baby is in care, plan on ~1–1.25 oz per hour, and split that into 2–4 oz bottles, plus one spare.
Does the amount of breast milk go up as my baby gets bigger?: Surprisingly, no — not the way formula does. Between about 1 and 6 months, a breastfed baby's daily intake stays roughly flat at 25 oz (750 ml) even as they double in weight. Breast milk changes in fat and calorie content over time to match your baby's growth, so they don't need to drink more. This is the biggest difference from formula, which is dosed by weight and keeps climbing.
Why not just use a formula calculator?: Because a formula calculator sizes bottles from your baby's weight — about 150 ml per kilogram per day — and that math doesn't apply to expressed breast milk, whose daily total stays flat from 1 to 6 months. Using a weight-based formula number for pumped milk usually overestimates how much a growing baby needs. If your baby is formula-fed or combination-fed, use the formula calculator for the formula portion and this tool for the breast-milk portion.
My baby takes much more (or less) than 25 oz a day. Is that normal?: Very likely yes. The 25 oz figure is an average; the normal range for exclusively breastfed babies runs from about 19 to 30 oz (570–900 ml) a day. Some babies take smaller, more frequent feeds and others larger, less frequent ones, and it evens out. As long as your baby is growing well and making plenty of wet diapers, the exact number matters less than the trend. Raise any worries about intake or supply with your pediatrician or a lactation consultant.
How much milk do I need to leave for an 8-hour work day?: For an 8-hour day, plan on roughly 8 to 10 oz (240–300 ml) total, using the ~1–1.25 oz per hour rule — then split it into three or four small bottles of 2–4 oz so nothing is wasted. Pump around the times your baby would normally feed to keep your supply matched to what's going out, and refrigerate or freeze what you express that day for the next one.