FORMULA CALCULATOR
Formula calculator by weight and age
How much formula your baby needs follows weight and age, not the calendar. This formula amount calculator applies the same rule pediatric guidance uses, and shows you the rule behind every number.
Last reviewed:
Your estimate
For a 10 lb baby, 4 months old
- Per day
- 20–40 oz
- Per feeding
- 6–8 oz
- Feedings per day
- 4–5
The AAP states a baby takes about 2.5 ounces (75 mL) of formula a day for every pound (453 g) of body weight. That is 25 oz for your baby.
The CDC says babies getting less than 32 ounces (about 950 mL) of formula a day need extra vitamin D drops, starting shortly after birth.
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Ranges by age
| Age | Per feeding | Feedings per day | Per day | Source |
|---|---|---|---|---|
| First days | 1–2 oz | 8–12 | 16–24 oz | [2] [1] [3] |
| First month | 3–4 oz | 6–8 | 18–32 oz(derived) | [2] [3] |
| 1 to 4 months | 4–6 oz | 4–6 | 16–36 oz(derived) | [2] [3] |
| 4 to 6 months | 6–8 oz | 4–5 | 20–40 oz | [3] [2] |
| 6 to 12 months | 6–8 oz | 4–5 | 24–40 oz(derived) | [2] [1] |
derived = per-feeding amount × feedings per day, where no daily total is stated.
How to use this formula calculator
Three entries are all the calculator needs. Everything below the form is the same arithmetic, done in the open, so you can check it against your own pediatrician's advice.
Enter the weight
Pounds, pounds and ounces, ounces, grams, or kilograms — whichever your scale reads. A home scale is accurate enough for a planning estimate; a weight from the last pediatric visit is better.
Enter the age
Days, weeks, or months. Age sets the feeding pattern and the per-feed range; weight sets the daily total. In the first month age matters most, because a newborn takes small feeds often no matter what the scale says.
Choose ounces or millilitres
The result converts instantly, so pick whichever unit your bottles are marked in. The ranges are identical either way; only the number on the screen changes.
How this is calculated
The tool does not guess. For each age it looks up the per-feed range and the number of feedings per day that the cited sources state, and multiplies them to get the daily range when the source does not give a daily total. The AAP weight rule is shown alongside as an independent cross-check.
The rule of thumb The AAP states a baby takes about 2.5 ounces (75 mL) of formula a day for every pound (453 g) of body weight. That is 25 oz for your baby. [2]
Vitamin D At 32 ounces (about 950 mL) or more of formula a day, the CDC says formula covers vitamin D and no extra drops are needed. [1]
From 12 months At 12 months you can move from infant formula to plain whole cow's milk. Do it gradually, replacing one formula feed at a time. No regular cow's milk before age 1. [1]
Upper limit The AAP says a baby should usually drink no more than an average of about 32 ounces (960 mL) of formula in 24 hours. If your baby consistently wants more or less than the ranges here, that is a conversation for your pediatrician. [2]
When this calculator is not enough
The estimate assumes a healthy term baby on standard infant formula. Four cases need your pediatrician's number instead of a calculator's.
Preterm or low birth weight
Volumes for babies born early follow corrected age and are often fortified. The standard weight rule does not apply, and the difference is large enough to matter.
Special or fortified formula
Higher- and lower-calorie formulas change how much volume delivers the same energy. Mix and measure exactly as prescribed, not as this estimate suggests.
Faltering weight or refused feeds
If weight is dropping, or your baby consistently takes far less than the range, the amount is not the real question. Call your pediatrician rather than pushing more volume.
Past the first birthday
The calculator stops at 12 months, when whole cow's milk and solid food take over the feeding plan.
Questions
- How much formula should a newborn drink?
- In the first days, the CDC suggests offering 1 to 2 ounces every 2 to 3 hours, with most formula-fed newborns feeding 8 to 12 times in 24 hours. MedlinePlus gives 2 to 3 ounces per feeding for a daily total of 16 to 24 ounces in that first stretch.
- Is there a simple formula for how much formula a baby needs?
- Yes. The AAP rule of thumb is about 2.5 ounces of formula per day for every pound of body weight. A 10-pound baby works out around 25 ounces a day. Treat it as a planning estimate, not a target to hit exactly.
- How many ounces should a 4-month-old drink?
- MedlinePlus puts 4 to 6-month-olds at 20 to 40 ounces of formula a day, with per-feed amounts climbing toward 6 to 8 ounces. That is also the window where many babies show signs of readiness for solid foods.
- Does a formula-fed baby need vitamin D drops?
- The CDC says babies getting about 32 ounces or more of formula a day do not need extra vitamin D, because formula is fortified. Below that, babies need vitamin D drops starting shortly after birth.
- Can I use this to work out breast milk amounts?
- No. This calculator covers infant formula. Breastfeeding works on demand rather than measured volumes, and the sources here give formula-specific guidance. Talk to your pediatrician or a lactation consultant about breastfed amounts.
- Is there a maximum amount of formula a baby should drink?
- Yes. The AAP says a baby should usually drink no more than an average of about 32 ounces (960 mL) of formula in 24 hours. Consistently wanting more or less than the typical range is worth raising with your pediatrician.
- Do different sources agree on amounts?
- Not exactly, and this tool does not hide that. The AAP puts the end of the first month at 3 to 4 ounces per feeding, while MedlinePlus says at least 4 ounces. Where sources differ, the table shows the wider range, and every row names the source it came from.
- What is a formula calculator?
- A formula calculator turns your baby's weight and age into a daily amount of formula and a per-feed split. It does the arithmetic on the rule pediatric guidance uses — about 2.5 ounces per pound per day — instead of leaving you to work it out on the back of the tub.
- Is a formula calculator accurate?
- It is a planning estimate, not a prescription. The weight rule describes a population average; intake moves with growth spurts, weather, and how much solid food an older baby is eating. Use the range as a starting point and let the growth curve and hunger cues correct it.
- Does this calculator work in mL?
- Yes. Switch the volume unit to mL and the per-feed and daily results convert. They are the same ounce ranges converted and rounded to whole millilitres, so they can land a millilitre or two away from a figure you work out by hand.
Track it in the app, not on a calculator
This is a planning range. The number that matters is what your baby actually takes. Log a feed in one tap and see today's total without adding anything up.
- ✓One tap to log a feed
- ✓Today's total, automatic
- ✓Share with the other caregiver
Sources
- [1]CDC, "How Much and How Often to Feed Infant Formula," reviewed April 21, 2026. cdc.gov ↗
- [2]AAP, "Amount and Schedule of Baby Formula Feedings," reviewed May 16, 2022. healthychildren.org ↗
- [3]MedlinePlus (U.S. National Library of Medicine), "Infant formulas," reviewed April 5, 2025. medlineplus.gov ↗
Accessed: 2026-10-06.
A planning estimate, not medical advice
This tool applies published guidance to the numbers you enter. Every baby is different. Use the result as a starting point and follow your pediatrician's advice for your baby.