Stages of Child Development

Child Development stages

As children grow, they go through a number of developmental stages. Each stage brings with it unique joys and challenges, and it can help to know what to expect. Additionally, understanding the typical developmental milestones for each stage can help you determine whether your child's development is on track or if you need to speak to your pediatrician.

Your Newborn


The WIC, from the USDA, keeps data about the average length and weight of all children, including newborns. According to the CDC, the average newborn girl weighs seven pounds and is about 20 inches long. The CDC reports that the average newborn boy is about seven and a half pounds and 19.5 inches long. If your baby is smaller or larger than average, this does not indicate a problem. There is significant variability in infant size, and a wide range of weights and lengths are considered healthy.

Your newborn is likely to be assessed by the medical staff within the first few minutes of birth and will continued to be scored and monitored while in the hospital. According to the Lucile Packard Children's Hospital at Stanford University and other experts, hospital staff will assess your baby's birth weight, alertness, breathing, and other important health factors. The following milestones are considered "normal" for newborns.

Physical Milestones

  • A breathing rate of around 30 to 60 breaths per minute
  • A head circumference, the distance around the head, that is around one-half the baby's body length plus 10 cm
  • A body temperature of 98.6° F (37° C) in a normal room environment

Social-Emotional Milestones

Cigna also describes some social-emotional traits often seen in newborn babies.

  • Uses facial expression to describe feelings
  • Face will brighten when seeing parents

Cognitive Milestones

Cigna also states that the newborn will have the following cognitive milestone:

  • Even babies who are only a few days old can mimic what their parents do, such as sticking out a tongue.

Your Two-Month-Old

2 months

The CDC reports that at two months old, the average baby girl will weigh about 11 pounds and be about 22.5 inches long. The average baby boy at the same age weighs about 12 pounds and measures 23 inches. Again, your baby may be larger or smaller, and your pediatrician will assess your child's length and weight during well-baby check-ups.

By the time your baby is two months old, he or she may reach the following milestones according to the trusted pediatrician, Dr. Sears.

Physical Milestones

  • More flexible body
  • React to sudden or loud noises
  • Make and hold eye contact
  • Hold head up
  • Roll from side-to-side

Social-Emotional Milestone

  • Smile
  • Track your movements with his eyes
  • Respond positively to being cuddled
  • Recognize and respond to your voice

Cognitive Milestones

  • Show a preference to certain toys
  • Explore his hands with his mouth
  • Express emotion when confronted with change

Your Three-Month-Old

tummy time

The CDC reports that the average three-month-old baby girl weighs about 13 pounds and is about 23 inches long. Average baby boys of the same age tip the scales at about 14 pounds and are about 24 inches long. Your baby may be smaller or larger.

Look for these milestones around your baby's third month, according to Child Development Institute Parenting Today.

Physical Milestones

  • Turn head at a 90-degree angle
  • Use arms to prop herself up
  • Visually track movement

Social-Emotional Milestone

  • Enjoys being held and acts content when with parents
  • Might be soothed by rocking

Cognitive Milestones

The makers of Similac say that a baby of this age usually meets these cognitive milestones:

  • Demonstrate some personality traits
  • Be aware of her surroundings

Your Six-Month-Old

baby sitting

At six months of age, the CDC reports that the average baby girl is about 15.5 pounds and 26 inches long. The average baby boy is 17 pounds and 26.5 inches. Your little one may be smaller or larger than average.

Your six-month-old baby is still growing rapidly and developing quickly and should reach these milestones, according to National Institute of Health.

Physical Milestones

  • Sit unassisted
  • Crawl or crab forward or backward
  • Support weight on legs and bounce

Social-Emotional Milestone

  • Fear strangers
  • Recognize her parents
  • Start saying one-syllable repeated sounds like "ba-ba"

Cognitive Milestones

  • Move items from one hand to the other
  • Imitate sounds
  • Babble to herself in the mirror

Your 12-Month-Old

baby walking

The first year is complete and your baby has grown a lot. According to the CDC, the average one-year-old baby girl will weigh about 20.5 pounds and be just over 29 inches long. The average one-year-old boy weighs about 21 pounds and measures about 30 inches.

Around his first birthday, The Center for Disease Control says that your baby may reach these developmental stages.

Physical Milestones

  • Wave good-bye and clap his hands
  • Start walking
  • Crawl expertly
  • Crawl up stairs

Social-Emotional Milestones

  • Respond to simple verbal requests
  • Have trouble sharing toys
  • Find it difficult to play with other children
  • Be possessive of her toys and personal items

Cognitive Milestones and other experts say that by her first birthday, your baby is likely to be able to:

  • Understand simple instructions
  • Imitate others' sounds and activities
  • Comb her own hair
  • Mimic the actions of adults, such as "reading" a book to her doll

Your 18-Month-Old

toddler coloring

According to the CDC, the average 18-month-old baby girl weighs about 22.5 pounds and measures 31.5 inches. The average baby boy of the same age weighs 24.5 pounds and measures 32.5 inches.

The Center for Disease Control gives some guidelines as to what a child of this age might be able to do around 18 months old.

Physical Milestones

  • Climb stairs with assistance
  • Get onto small chairs without help
  • Has some control over the muscles used for going to the bathroom
  • Walk unassisted

Social-Emotional Milestones

  • Imitates the behavior of adults and older children
  • Is able to show affection
  • Has a sense of ownership

Cognitive Milestones

  • Say about 15 to 20 words
  • Feed himself with a spoon
  • Point to several body parts upon request
  • Scribble on paper with a crayon

Your Two-Year-Old


At the age of two years, the CDC reports that the average girl weighs about 25 pounds and is about 34 inches tall. The average boy of the same age is about 27 pounds and 34.5 inches tall.

According to, by his second birthday, your child may be able to do the following.

Physical Milestones

  • Kick a ball
  • Pull toy behind her while walking
  • Walk on her own
  • Starts to run
  • Might show a preference to one hand or another
  • Stand on her tip-toes

Social-Emotional Milestones

  • Increasingly enthusiastic about company of other children
  • Begins to show defiant behavior
  • Increasingly aware of herself as separate from others

Cognitive Milestones

  • Follow two-step directions
  • Name pictures in books
  • Can finds objects that are under a blanket
  • Sorts objects by shapes and colors
  • Form three and four word sentences
  • Have a vocabulary of at least 25 words

Your Three-Year-Old


According to the CDC, the average three-year-old girl weighs about 30 pounds and is about 37 inches tall. The average boy of the same age weighs about 32 pounds and is 37.5 inches tall.

The Child Development Institute and The CDC suggests that children who are around three years old may be able to do these milestones.

Physical Milestone

  • Pedal a three-wheel bike (tricycle)
  • Stand on one leg

Social-Emotional Milestone

  • Starts showing sense of humor
  • Begin playing more cooperatively with other children
  • Communicate wants and needs verbally and can be understood most of the time

Cognitive Milestone

  • Does puzzles with three or four pieces
  • Have a longer attention span
  • Be more independent with self-care skills like dressing, washing hands, and brushing teeth

Your Pre-Schooler or Kindergartner


According to the CDC, the average preschooler or kindergartner has the following height and weight:

  • For four-year-old girls, the average weight is 35 pounds, and the average height is 39.5 inches.
  • For four-year-old boys, the average weight is 36 pounds, and the average height is 40.5 inches.
  • For five-year-old girls, the average weight is 39.5 pounds, and the average weight is 42.5 inches.
  • For five-year-old boys, the average weight is 41 pounds, and the average weight is 43 inches.

The CDC and other experts say that pre-schoolers and kindergartners should be able to do the following.

Physical Milestones

  • Hop and stand on one foot for up to two seconds
  • Catch a bounced ball most of the time
  • Pour
  • Cut with supervision
  • Walk up and down the stairs
  • Kick a ball
  • Run easily
  • Pedal a tricycle
  • Bend over without falling over
  • Take turns when playing a game
  • Play make-believe

Social-Emotional Milestones states that pre-schoolers and kindergartners are likely to do the following:

  • Develop friendships
  • Start understanding the concept of sharing
  • Need encouragement to share and consider others

Cognitive Milestones also says that kids of this age group should be able to do the following:

  • Copy a square and a triangle
  • Talk clearly
  • Use adult speech sounds
  • Know basic grammar
  • Retell a story
  • Have a vocabulary of over 2,000 words
  • Say first and last name

Your Elementary School Age Child

school kids

During the elementary school years, your child will grow and develop rapidly. During these years, their weight and height begin to vary dramatically. The CDC offers data about the average height and weight for children of every age, but it's important to remember that these numbers are only averages. Your child may be taller or shorter, heavier or lighter, than the average range.

Age Average Weight for Girls Average Weight for Boys Average Height for Girls Average Height for Boys
6 44.4 pounds 45.3 pounds 45.2 inches 45.2 inches
7 49.9 pounds 50.6 pounds 47.6 inches 48 inches
8 56.3 pounds 56.3 pounds 50.1 inches 50.4 inches
9 63.8 pounds 62.7 pounds 52.3 inches 52.6 inches
10 72.3 pounds 70.4 pounds 54.3 inches 54.5 inches

Physical Milestones and The CDC give some milestones that your elementary school age child may be able to do:

  • Bounce, throw and catch a ball
  • Ride a bicycle
  • Tie shoelaces

Social-Emotional Milestones

  • Are interested in hanging-out with a peer group
  • Have a need to belong
  • Are influenced by peers in the way the dress and talk

Cognitive Milestones

According to WebMD, your elementary school child should reach the following cognitive milestones:

  • Begin reading simple books by the end of first grade
  • Recognize basic object shapes by first grade
  • Write simple stories by second grade
  • Understand money and time by second grade
  • Be able to read easily on their own by the end of third grade
  • Multiply, divide, and do fractions by fourth grade

Your Middle or High Schooler

teen girls

In middle and high school, kids are growing and developing at different rates. Puberty may hit some teens earlier than others, so instead of using height and weight to gauge kids' growth, it's better to go with body mass index (BMI). To calculate BMI, simply take the teen's weight (measured in kilograms) and divide it by his or her height (measured in meters). According to the CDC, these are the average BMIs for kids aged 11 through 18. Since these are only averages, your healthy child may have a BMI that is slightly higher or lower.

Age Average BMI for Girls Average BMI for Boys
11 17.4 17.1
12 18.1 17.8
13 18.7 18.4
14 19.3 19.1
15 19.9 19.8
16 20.4 20.5
17 20.9 21.2
18 21.2 21.8

Physical Milestones

During adolescence, kids reach puberty at different ages. According to WebMD, this is a process that involves several milestones and can take years. Expect the following:

  • Girls may begin puberty as early as eight years old and continue developing until the age of 16. Changes include growing taller, getting wider hips, developing breasts, beginning menstruation, growing hair on the genitals and underarms, and other physical developments.
  • Boys can start puberty as early as nine years old and finish the process at the age of 18. Boys will get deeper voices, grow taller, develop musculature, grow hair on genitals and underarms, and become sexually mature.

According to the, girls will continue to slowly gain gross motor skills until the age of 14, and boys will encounter a dramatic improvement in gross motor skills during the teen years.

Social-Emotional Milestones

According to the University of Alabama, your teen may also experience these social-emotional milestones:

  • He or she may feel like there is an imaginary audience watching (and judging) every move.
  • Your pre-teen or teen may feel immortal or invulnerable to injury or death, leading to an increase in risky behaviors.
  • Teens may try out different values and identities as they try to find out who they are.
  • Friends become even more important and may have an influence on what your child thinks and does.

Cognitive Milestones

During the adolescent stage, the University of Alabama reports that your child may go through the following cognitive milestones:

  • Increase in abstract thinking
  • Improved ability to formulate an argument
  • Improved verbal and math skills

If You Have Concerns

Every child develops at his or her own unique pace, and parents should try not to compare their child to his siblings or other people's children. However, if you are concerned about your child's development and you notice that he or she is not keeping up with milestones, it's a good idea to seek help.

  • Start by explaining your concerns to your child's pediatrician. He or she can advise you about the steps to take to have your child evaluated and receive help through therapy or other assistance that may be necessary.
  • You can also talk to your school district. If you're child is already in school, speak to his or her teacher for a recommendation, and submit a written request to the school that they assess your child. If your child hasn't begun school yet, you can still get help from the school district with an early intervention program. Simply call your school's special education department to get started.
  • Keep records of your child's development, including a growth chart and a list of the ages when he or she met the developmental milestones. This will help your doctor or school determine if there is a consistent delay.
  • Understand that children can have "splintered skills," meaning they can be on track or even ahead in some areas and behind in others. Getting help for your child can give him or her the best chance to catch up to peers.
  • Try to challenge your child at home in the areas that seem to be a struggle. For instance, to get a baby to crawl, place objects just out of his or her reach. Lots of parent involvement and encouragement can dramatically improve your child's skills in areas that are challenging.

Your Child Is Unique

Every child develops at a different rate, and there is a wide range of what is considered "normal" development. Don't worry if your child walks or talks later than someone else's child. Your child is unique and his development will be unique as well. If you are concerned, it is wise to talk with the child's doctor who can do further evaluation.

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