The amount a newborn needs to eat isn’t an exact science, because every baby is different. However, there is a simple equation you can use to get a rough estimate of how many ounces your baby needs each day. Remember that an infant’s needs can change day-to-day. While having a rough estimate of how much formula they need can be helpful, it’s most important to learn and respond to your baby’s hunger and fullness cues.

Signs of Hunger and Fullness

Whether you’re using a formula, nursing, pumping, or a combination of all these feeding methods, tune in to your baby’s hunger and fullness cues before you start crunching numbers. While each baby is unique, these are are some common hunger cues to watch for:

  • Crying or fussinessOpening of his mouth when touched on his chin or lipsSmacking of lips or making small sounds with his mouthSucking on fingers or placing fist in mouth

Fullness cues include:

  • Fidgeting or acting distractedSlowing down or falling asleepSpitting out formulaStopping feeding or only taking a few sucks before pausing

How to Calculate Formula Needs

In addition to looking for cues to when your baby is hungry and when they’ve had enough, you can use different techniques to estimate the amount of formula to prepare. But again, from one day to the next, your baby may want more or less at any feeding. So watching for hunger/fullness cues is important.

By Weight

This equation can be used regardless of what type of infant formula you use (cow milk formula, soy-based formula, etc).

Most babies are satisfied with 3 to 4 ounces per feeding in the first month. You’ll begin to increase the amount by 1 ounce per month, leveling off at about 7 to 8 ounces per feeding.

According to the American Academy of Pediatrics (AAP), a baby should consume, on average, about 2.5 ounces of formula a day for every pound of their body weight.

For example, a 12-pound baby would likely need 30 ounces in a 24-hour period. To determine how many ounces per bottle, divide the ounces needed in a 24-hour period by the number of feedings your baby takes during that time. So, if your 12-pound baby needs 30 ounces a day and takes 6 bottles in a 24-hour period, then each bottle would need to be approximately 5 ounces.

By Age

You can also estimate formula needs by your infant’s age.

  • Newborns: 2 to 3 ounces per feedingOne month: 4 ounces per feedingTwo months: 4 to 5 ounces per feedingFour months: 4 to 6 ounces per feedingSix months: 6 to 8 ounces per feeding

Signs of Over- or Under-feeding

Signs that you are not feeding your baby enough can include persistent crying, decreased urine output, a wrinkly look to the skin, dry roof of the mouth, and increased sleep. Your baby should be wetting at least four diapers a day. Their bowel movements should be no firmer than peanut butter. Hard or dry stools can be a sign that your baby is not adequately hydrated.

Generally speaking, it’s best to time feedings to allow your baby to take bottles that have less formula, which means you’ll be giving them more frequently (as opposed to giving larger amounts of formula less often). If you are concerned about your baby’s weight or if you think they are losing or gaining weight too rapidly, talk to your pediatrician.

Signs that you might be overfeeding may include spitting up or vomiting, crying, pulling up legs to the abdomen, and behaviors that resemble colic.

  • American Academy of Pediatrics. Amount and schedule of formula feedings.

  • Shelov SP, Altmann TR, Hannermann RE. Caring for your baby and young child, birth to age 5, 6th Edition. American Academy of Pediatrics.

  • American Academy of Pediatrics. Is your baby hungry or full? Responsive feeding explained.

  • American Academy of Pediatrics. How often and how much should your baby eat?.

  • American Academy of Pediatrics. Amount and schedule of formula feedings.

By Jennifer White

Jennifer White has authored parenting books and has worked in childcare and education fields for over 15 years.