How old is an infant? An infant is a baby from birth to 12 months of age, and the infant age range ends on the first birthday, when a child becomes a toddler.
It sounds like a simple question, but the words newborn, infant, baby, and toddler are used in different ways by doctors, airlines, clothing brands, and day cares. That can make labels and guidelines confusing.
This guide explains the infant age range, shows how each term is defined, breaks infancy into its stages, and covers the health and safety guidelines that change at 12 months.
Key Takeaways
An infant is a child from birth to 12 months old.
A newborn is an infant in the first 28 days of life, or the first 2 to 3 months in everyday speech.
“Baby” is an informal word with no official age cutoff.
A toddler is a child from 1 to 3 years old.
Key guidelines on safe sleep, milk, and honey are tied to the 12 month mark.
Table of Contents
How Old Is an Infant?
Quick Answer
An infant is a child from birth to 12 months old. A newborn is an infant in the first weeks of life (medically, the first 28 days). After the first birthday, a child is usually called a toddler.
The word comes from the Latin infans, meaning “unable to speak,” which fits: infancy is the stage before walking and talking take off. In the United States, the Centers for Disease Control and Prevention (CDC) groups children as infants from 0 to 1 year, toddlers from 1 to 3 years, and preschoolers from 3 to 5 years. Public health statistics follow the same line. Infant mortality, for example, counts deaths before a child’s first birthday.
So if you are filling in a form, reading a product label, or wondering which milestone chart applies, the infant age range is birth through 11 months, ending on the first birthday.
Infant Age Range Chart: Newborn, Infant, Baby, Toddler
These terms overlap in everyday speech. Here is how they are typically defined:
Term
Age range
Notes
Newborn (neonate)
Birth to 28 days
The medical definition used by the World Health Organization. In everyday use, often the first 2 to 3 months.
Infant
Birth to 12 months
The CDC and most health sources use 0 to 1 year. Includes newborns.
Baby
Birth to about 12 months
An informal word with no official cutoff. Many parents use it well into the toddler years.
Toddler
1 to 3 years
Begins around the first birthday, when many children start to “toddle.”
Preschooler
3 to 5 years
The years before kindergarten.
Infant age range compared with newborn, baby, toddler, and preschooler.
Every newborn is an infant, but not every infant is a newborn. And “baby” is simply the friendly word for both.
The Stages of Infancy
Twelve months is a long time in a baby’s life. Many pediatric sources break infancy into smaller stages:
Newborn (0 to 2 months): sleeping and feeding around the clock, strong reflexes, and first social smiles by about 2 months. See our newborn sleep schedule and 1 month old milestones.
Young infant (2 to 4 months): better head control, cooing, tracking faces, and longer stretches of night sleep for some babies.
Middle infancy (4 to 8 months): rolling over, sitting with support and then alone, babbling, and starting solid foods at about 6 months. See when babies roll over and our guide to starting solids.
The 12 month line is more than a label. Several important health and safety guidelines are tied to it:
Safe sleep: the American Academy of Pediatrics (AAP) recommends back sleeping on a firm, flat, bare surface for the entire first year. See our guide to a safe sleep environment.
Feeding: breast milk or infant formula is the main drink for the first 12 months. Cow’s milk as a drink waits until the first birthday.
Honey: no honey before 12 months, because of the risk of infant botulism.
Solid foods: introduced at about 6 months, when a baby shows signs of readiness.
Water: small sips with meals from about 6 months. Younger infants get all the fluid they need from breast milk or formula.
Sleep needs: the American Academy of Sleep Medicine recommends 12 to 16 hours of sleep per 24 hours, including naps, for infants 4 to 12 months old.
Checkups: infants have frequent well-child visits, typically in the first week and at 1, 2, 4, 6, 9, and 12 months.
After the first birthday, the guidance shifts. Toddlers need 11 to 14 hours of sleep, can drink whole milk, and eat mostly family foods.
When “Infant” Means Something Different
Outside of medicine, the word infant is used more loosely. A few common examples:
Airlines: a “lap infant” is usually a child under 2 years old who travels on an adult’s lap.
Car seats: an “infant car seat” is defined by the seat’s weight and height limits, not by age. Many babies outgrow one before or soon after their first birthday. See what car seat comes after the infant seat.
Child care: an “infant room” often covers babies from about 6 weeks to 12 or 18 months, depending on the center and state rules.
Clothing: “infant” sizes commonly run from newborn through 24 months. See our baby clothes size chart.
Medicine labels: products labeled for infants may list a different age range, and dosing is based on weight. Always check with your pediatrician before giving medicine to a baby.
Formula: U.S. regulations define an infant as a person not more than 12 months old, which is why infant formula is designed for the first year.
Law: in some legal contexts, “infant” can mean any minor. That use has nothing to do with child development.
When a label or policy uses the word infant, check the fine print for the actual age, weight, or height range.
Newborn vs. Infant: What Is the Difference?
A newborn is the youngest kind of infant. Doctors use the term neonate for the first 28 days, a period with its own medical care, screening tests, and risks. In everyday speech, parents and baby brands stretch “newborn” to cover roughly the first 2 or 3 months, the so-called fourth trimester.
The practical differences are large. Newborns sleep in short bursts day and night, feed 8 to 12 times in 24 hours, have little head control, and see best at close range. By the middle of infancy, the same baby is awake for longer stretches, eating on a more predictable pattern, laughing, and reaching for toys. Our guide to newborn vision and our infant activities list show how quickly things change.
When Does an Infant Become a Toddler?
On paper, at 12 months. In real life, the change is gradual. The word toddler comes from “toddle,” the unsteady walk of a child who is just finding their feet. Most children take their first independent steps between about 9 and 15 months, so some infants walk early and some new toddlers are still crawling.
Stronger opinions, and the first signs of wanting to do things alone.
Your child does not stop being your baby on their first birthday. The label changes because their needs do.
Adjusted Age for Babies Born Early
If your baby was born before 37 weeks, their development is tracked by adjusted age, also called corrected age. To find it, take your baby’s age since birth and subtract the number of weeks they were born early. A baby who is 6 months old and was born 2 months early has an adjusted age of 4 months.
The AAP advises using corrected age when looking at developmental milestones, generally until about age 2. Your baby is still an infant for 12 months from their birth date for things like safe sleep and formula. Adjusted age simply gives a fairer picture of when to expect skills like rolling, sitting, and walking.
Labels matter far less than your individual child. Talk to your pediatrician if your infant is not meeting several milestones for their age, loses a skill they once had, is not gaining weight as expected, or if you simply have a feeling that something is off. The CDC’s milestone checklists are a helpful guide for what to look for at 2, 4, 6, 9, and 12 months.
Regular well-child visits are the best place to ask these questions. No concern is too small.
Frequently Asked Questions
How old is an infant?
An infant is a child from birth to 12 months old. The CDC groups infants as 0 to 1 year, toddlers as 1 to 3 years, and preschoolers as 3 to 5 years.
What is the infant age range?
The infant age range is birth through 11 months, ending on the first birthday. It includes the newborn period, which medically covers the first 28 days of life.
Is a 1 year old an infant or a toddler?
A 1 year old is a toddler. Infancy ends at the first birthday, and the toddler stage runs from 1 to 3 years.
What is the difference between a newborn and an infant?
A newborn is an infant in the first weeks of life. Medically, the newborn or neonatal period is the first 28 days. Infant covers the whole first year, so every newborn is an infant.
Is a 2 month old a newborn or an infant?
Both words are used. Medically, a 2 month old is an infant, since the newborn period ends at 28 days. In everyday speech, many people still call a 2 month old a newborn.
At what age is a baby no longer a baby?
There is no official age. “Baby” is an informal word. Most sources switch to “toddler” at 12 months, but many families keep saying baby for much longer.
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