Breast Milk Calculator
Find out roughly how much expressed breast milk to put in each bottle and how much your baby takes in a day, based on age and number of feeds. Add the hours you'll be away to see how many bottles to leave and how often to pump.
Last updated:
0–15 oz
Work + commute; 0 to skip the bottle plan
How to use the Breast Milk Calculator
- Choose units and enter your baby's weight.
- Enter the age in days, weeks or months.
- Pick feeds per day or keep the typical number for that age.
- Add hours away (work plus commute) to get a bottle and pumping plan, or enter 0.
- Read the per-bottle amount and use it as a starting point, adjusting to your baby's cues.
How the breast milk amount is estimated
Unlike formula, breast milk intake doesn't rise steadily with weight. Studies of exclusively breastfed babies found that, after the first month, daily intake settles at an average of about 750 ml (25 oz) and usually stays in a range of 570–900 ml (19–30 oz) until solids start. The calculator uses these age bands:
- First week: a few ml of colostrum per feed on day 1, about 22–27 ml on day 3, and about 45–60 ml by day 7.
- Weeks 1–5: a gradual rise from about 450 ml (15 oz) to 750 ml (25 oz) a day.
- 1–6 months: about 750 ml (25 oz) a day.
- 6–12 months: intake slowly falls as food increases. WHO estimates average intakes of about 615 ml at 6–8 months and 550 ml at 9–11 months.
Per bottle = daily amount ÷ feeds per day. Example: a 10-week-old who feeds 8 times a day needs about 750 ÷ 8 ≈ 94 ml (3.2 oz) per bottle.
Bottle size by feeds per day (1–6 months)
| Feeds a day | Interval | Average per bottle | Typical range |
|---|---|---|---|
| 6 | every 4 h | 4.2 oz (125 ml) | 3.2–5.1 oz |
| 7 | every 3.4 h | 3.6 oz (107 ml) | 2.8–4.3 oz |
| 8 | every 3 h | 3.2 oz (94 ml) | 2.4–3.8 oz |
| 9 | every 2.7 h | 2.8 oz (83 ml) | 2.1–3.4 oz |
| 10 | every 2.4 h | 2.5 oz (75 ml) | 1.9–3 oz |
Tips for bottle-feeding pumped milk
- Start small. Offer a bottle at the lower end of the range and add an extra 0.5–1 oz top-up if your baby still seems hungry. Leftover milk from a feed shouldn't be saved for the next one.
- Pace the feed. Holding the bottle more horizontally and pausing every few minutes lets your baby control the flow, more like at the breast, and helps avoid overfeeding.
- Freeze in small portions. Storing milk in 2–4 oz portions means less waste and quicker thawing.
- Watch the baby, not the bottle. Steady weight gain, contentment after feeds and plenty of wet diapers matter more than hitting an exact number.
Frequently asked questions
How much breast milk does a baby need per bottle?
Between 1 and 6 months most breastfed babies take about 25 oz (750 ml) a day in total, so the bottle size is that amount divided by the number of feeds. With 8 feeds a day that is about 3 oz (90–95 ml) per bottle; with 6 feeds about 4 oz (125 ml).
Does a breastfed baby need more milk as they get bigger?
Not much between about 1 and 6 months. Research on exclusively breastfed babies shows daily intake stays fairly steady at around 19–30 oz (570–900 ml) a day in that period, because growth slows and breast milk changes composition. Formula-fed babies tend to take more as they grow.
Why is breast milk intake different from formula?
Breastfed babies control how much they take, and breast milk's makeup changes during a feed and over time. Formula guidance is usually weight-based (about 2.5 oz per lb a day), which can overestimate what a breastfed baby needs from a bottle.
How much milk should I leave for daycare?
Count the feeds your baby would normally have while you are apart. For a typical 3-month-old fed every 3 hours and away for 9–10 hours, that is about 3–4 bottles of 3–4 oz, or roughly 10–13 oz in total. Offering smaller bottles avoids wasting milk.
How much milk does a newborn take in the first week?
Very little at first: colostrum on day 1 is only a few ml per feed (often 30–60 ml in the whole day). By day 3 many babies take about 0.75–1 oz (22–30 ml) per feed and by the end of the first week about 1.5–2 oz (45–60 ml).
How often should I pump while away from my baby?
A common guide is to pump about as often as your baby would feed, roughly every 3 hours, to protect your supply and replace the bottles your baby drinks.
Is this calculator medical advice?
No. It gives general averages for healthy, full-term babies. Signs of enough milk include steady weight gain and around 6 or more wet diapers a day after the first week. Ask your pediatrician or a lactation consultant about premature babies or feeding concerns.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.