What this calculator does
A breast milk calculator ml/kg guideline is one way to get a rough sense of how much a breastfed baby might be taking in, using published intake ranges from the first days of life through to around six months. It converts a weight, an age band and a number of feeds per day into an estimated daily volume and an amount per feed.
Breastfed intake does not behave the same way across the whole of infancy. In the first one to two weeks it ramps up quickly as milk supply establishes, roughly in line with weight. From about two weeks to six months, total daily intake for a healthy, exclusively breastfed baby tends to level off at a fairly constant volume rather than continuing to climb with weight, which is a different pattern to formula feeding guidelines.
The formula
For the first two weeks, daily volume is estimated as weight in kilograms multiplied by an age-based mL/kg guideline that rises from around 60 mL/kg on day 1 to around 150 mL/kg by day 10-13. From roughly two weeks to six months, daily volume is instead held at an approximately constant total of about 750-800 mL/day, reflecting how breastfed intake plateaus rather than keeps scaling with weight. Dividing the daily total by the number of feeds gives the per-feed estimate.
| Term | Meaning |
|---|---|
| mL/kg guideline | A published intake rate, expressed per kilogram of baby weight, used only in the first one to two weeks while supply is still ramping up. |
| Plateau volume | The roughly constant total daily intake, around 750-800 mL, typical of exclusively breastfed babies from about two weeks to six months regardless of further weight gain. |
| Per-feed volume | The estimated daily total divided evenly across the number of feeds entered, useful for expressing pumped or expressed milk in bottle-sized amounts. |
The inputs explained
| Field | What to enter |
|---|---|
| Baby weight (kg) | The baby's current weight in kilograms. |
| Age | Select the age band that matches the baby: a specific early day for the ramp-up period, or the 2 weeks to 6 months plateau band. |
| Feeds per day | How many times the baby feeds in a 24-hour period, used only to split the daily total into a per-feed amount. |
When to use it
Checking a newborn is on track in the first fortnight
In the first one to two weeks, intake is expected to rise day by day as milk supply increases. Comparing an estimated daily volume against actual feeding patterns can help flag whether things are tracking in the expected direction, alongside wet nappy counts and weight checks.
Working out bottle sizes for expressed milk
A parent expressing milk for a carer or childcare needs to know roughly how much to put in each bottle. Dividing an expected daily total by the number of feeds gives a starting point, which can then be adjusted based on what the baby actually takes.
Understanding why intake stops rising with weight
Once a baby is a couple of weeks old, growth continues but breast milk intake generally does not keep climbing at the same rate. Seeing the plateau figure alongside the ramp-up figures makes that shift explicit rather than confusing.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Estimated per-feed volume across the first fortnight, at a fixed weight
The same weight and feed count, across the early-day guideline bands.
| Age band | Daily breast milk volume | Per feeding (8x/day) |
|---|---|---|
| Day 1 | 240 mL | 30 mL |
| Day 3 | 400 mL | 50 mL |
| Day 7 | 560 mL | 70 mL |
| Day 10-13 | 600 mL | 75 mL |
Per-feed volume during the 2 weeks to 6 months plateau, by feeds per day
The same roughly constant daily total, split across different numbers of daily feeds.
| Feeds per day | Daily breast milk volume | Per-feed volume |
|---|---|---|
| 5x | 775 mL | 155 mL |
| 6x | 775 mL | 129 mL |
| 7x | 775 mL | 111 mL |
| 8x | 775 mL | 97 mL |
| 10x | 775 mL | 78 mL |
| 12x | 775 mL | 65 mL |
Questions
Why doesn't breast milk intake keep increasing with weight after two weeks?
Once supply is established, exclusively breastfed babies tend to take in a fairly steady total daily volume for months, even as they continue gaining weight, unlike bottle-fed volumes which are often calculated per kilogram throughout infancy. Growth in this period comes from the baby extracting milk more efficiently and from changes in milk composition, not from steadily larger daily volumes.
How is this different from a formula intake calculator?
A formula-feeding calculator scales the daily volume with weight the whole way through, because formula guidelines are generally expressed as a fixed rate per kilogram at any age. Breast milk intake instead ramps up briefly in the first fortnight and then plateaus at a roughly constant total, which this calculator reflects with a separate plateau band.
Is this a reliable way to know if my baby is getting enough?
No, treat it only as a rough guide. The most reliable signs that a breastfed baby is getting enough milk are steady weight gain, plenty of wet and dirty nappies, and a satisfied baby after feeds. Speak with a health professional, midwife or lactation consultant if you have any concerns.
Does this apply to combination or exclusively pumped feeding?
The plateau figures are based on exclusively breastfed babies. A baby getting a mix of breast milk and formula, or being exclusively pumped and bottle-fed, may take somewhat different volumes, so use this as a starting estimate rather than a precise target.
For a bottle-fed baby, see the baby formula daily intake calculator, which uses a weight-scaled guideline throughout. To work out a baby's age in days, weeks or months for tracking growth, see the age calculator.