It is important to monitor your baby’s growth and development. When it comes to the weight of your baby in his or her first year, there is a wide range of normal. Babies may be healthy in the 5th, or 50th percentiles. Healthy babies can be of any size.
At every checkup, your child’s doctor will weigh them. They’ll also measure their head circumference and length, and track how they are progressing with their developmental milestones. Most important? Most important? They will measure your baby’s progress over time. They will look at the overall curve of growth throughout the first year, and detect any deviations. Our reference guide can help you find out your baby’s weight average by month. We’ll also discuss the importance of sleep and feeding patterns in a healthy growth.
Note from the Editor: If you are concerned about your baby’s growth or health, contact your child’s doctor.
Weight of a baby at one month.
Your little one will go through some remarkable changes during the first month. In the first week of life, newborns lose a little bit of their birthweight. They quickly gain it back (thanks in part to constant feeding) and should then continue to grow steadily. Infants gain an average of one ounce a day in the first month.
WHO and CDC report:
A baby boy who is 1 month old and in the 50th per centile weighs approximately 9 pounds 14 ounces.
A baby girl weighing 9 pounds 4 ounces in the 50th centile is 4.2 kilograms.
Nutrition and feeding
Does your baby seem to be hungry all the time? This may seem to be the case. Although the stomach of a baby is small, it grows every day. In the first week, breast milk or formula is usually consumed every 2-3 hours.
Sleep patterns
Remember that your baby’s sleeping schedule shouldn’t be a strict one just yet. You can prevent overtiredness by paying attention to sleepy cues, such as rubbing the eyes, fussiness or staring into space. If you are holding them to nap (also known as contact napping), is that okay? It’s fine.
Refer to the 1-month-old Baby Health & Growth Guide
Factors that affect baby weight
The weight of your baby is affected by several factors, including
Size at birth: Your baby’s weight at birth can affect their weight for the first year.
At birth, males tend to be heavier than females and gain weight faster.
Babys born early or full-term may weigh less compared to babies born late or full-term.
According to the AAP, breastfed babies gain weight faster than babies who are formula-fed in their first six months of life.
Average weight of a baby in the second and third months
Your baby’s rapid growth will continue as they enter the second and third month. The development of motor and cognitive skills is also accelerating. Your little one is more aware of their environment, can use his hands more, recognizes faces they know, and even smiles and coos (swoon!) Your baby can gain between 5 and 7 ounces a week in the second and third months.
Below you will find the average weight as determined by the WHO and CDC.
Average weight at 2 months
A baby boy 2 months old in the 50th per centile weighs 12 lbs, 5 ounces (5.8 kilograms).
A baby girl who is 2 months old and in the 50th per centile weighs 11 pounds 4 ounces (5 kilograms).
Baby Growth & Health Guide for 2-Month-Old Babies
Average weight at 3 months
A baby boy 3 months old in the 50th per centile weighs approximately 14 pounds (6.4 kg).
A baby girl aged 3 months in the 50th per centile weighs 12.14 ounces or 5.8 kilograms.
Related: Growth & health of a 3-month-old infant
Nutrition and feeding
While your baby’s 8-week-old feeding schedule may be becoming more organized (you can predict their hunger better), don’t set strict schedules yet. Your infant may also experience a few growth spurts during this period. Cluster feeding is characterized by rapid and sudden growth, an increased appetite and frequent feeding. It is normal to notice increased night wakings, fussiness and more frequent feedings. However, growth spurts are usually only lasting a few days.
Sleep patterns
As a 2-month-old, your baby is still a newborn and will still sleep most of the time. By 3 months their night sleep might have consolidated a bit. Sleeping patterns for your 3-month old child are not yet set in stone. This will happen closer to the fourth month. Aim for three to five naps per child each day.
Baby length factors
Your baby’s future height and length is affected by several factors:
Height of parents: The heights of the baby’s parents, and those in their family, will have a significant impact on his or her future height.
Nutrition: Adequate nutrition can result in strong bones and muscles.
Chronic diseases in childhood can have a negative impact on future growth and development.
At birth, males are slightly taller.
Average weight of babies in the fourth, fifth and sixth months
Your baby will become more curious in months 4 to 6 and want to learn about their environment. During these months, your baby’s motor skills will be developing rapidly. They may begin to roll over and gain improved head and neck control. Many babies will double their birthweight by 4 or 5 month. In months 4 and 5 you can expect to see your baby gain an additional 1 to 1.25 pounds. Growth will slow after 6 months (but only slightly). Also at six months? Start solids! Consult your pediatrician for a smooth transition from liquid to solid food.
The average weight of a person according to WHO and CDC is shown below.
Average weight at 4 months
A baby boy who is 4 months old and in the 50th per centile weighs 7 kilograms (15 pounds).
A baby girl who is 4 months old and in the 50th per centile weighs approximately 14 pounds 2 ounces (6 kilograms).
Guide to the health and growth of a 4-month-old infant
Average weight at 5 months
A baby boy 5 months old in the 50th per centile weighs 16 lbs, 9 ounces (7 kilograms).
A baby girl who is 5 months old and in the 50th per centile weighs 15.3 pounds, 3.0 ounces (6.9 kg).
Health & Growth Guide for 5-Month-Old Babies
Average weight at 6 months
A baby boy aged 6 months in the 50th per centile weighs 17.8 pounds (8.9 kilograms).
A baby girl aged 6 months in the 50th per centile weighs 16 lbs, 2 ounces (7 kilograms).
Baby Growth & Health Guide for 6-Month-Old Babies
Nutrition and feeding
Breast milk or formula is the best source of calories and nutrients for your baby during his first year. Around the 6-month-mark, you will want to encourage them to try new foods and explore different textures while still providing nutrition through breast milk or formula.
The AAP and La Leche League recommend that 5-month-olds be fed according to the schedule and amounts recommended below.
Breast milk: 5-7 ounces every three to four hours
Formula: 5-6 ounces every four to five hours
Sleep patterns
Your baby’s wake window is now even longer, allowing for more playtime, outdoor walks, and tummy-time. According to the American Academy of Sleep Medicine, you should aim for 12 to 16 total hours of sleep in a 24-hour period, with 10 to 12 hours of nightly sleep.
The 4-month sleep regression may be causing your infant to wake up more at night, or have difficulty settling for sleep. However, re-framing this regression as a progress can help make the period less stressful. There’s a reason for all the chaos: your child is increasing melatonin and making big developmental leaps. Focus on maintaining a consistent routine at bedtime and you will see that it passes.
Growth charts and percentiles: What you need to know
The pediatrician plots your child’s weight, height and head circumference onto a growth chart. This is the same chart that they have used since the day they were born. Growth charts are used to show your child’s growth over time. They can also be used to compare your baby’s length or weight with other babies of the same age.
Let’s say, for example, that your baby’s birth weight falls in the 75th per centile. This means that 25 percent of babies the same age, gender and weight weigh more and 75 percent weigh less. All babies are healthy and grow at their own rate. Your child’s doctor will look at the growth curve or overall pattern of your child’s growth chart in order to ensure that they are showing steady and sustained growth.
Average weight of a baby in the months 7, 8, and 9
Growth slows down in the last six months of the year. Your baby’s growth is accelerating. In months 7 to 9 your lovebug is likely to reach major developmental milestones, such as crawling, standing up, or even saying their first words. This is a very exciting time.
The average weight of a person according to WHO and CDC is shown below.
Average weight at 7 months
A 7-month old baby boy who is in the 50th per centile weighs 18.5 pounds, 5 ounces (8.1 kilograms).
A 7-month old baby girl who is in the 50th per centile weighs 16.4 pounds, 14.4 ounces (7.6 kg).
Related: 7-month old baby health and growth guide
Average weight at 8 months
A baby boy 8 months old in the 50th per centile weighs 19.6 pounds (8.6 kg).
A baby girl 8 months old in the 50th per centile weighs 17.7 pounds (7.9 kilograms).
Health & Growth Guide for 8-Month-Old Babies
Average weight at 9 months
A 9-month old baby boy who is in the 50th per centile weighs 19.9 kilograms.
A 9-month old baby girl who is in the 50th per centile weighs 18.2 pounds and 2 ounces.
Related: Growth & health of 9-month-old babies
Nutrition and feeding
You can now start to experiment with different combinations of food, such as vegetables, fruits, grains, and proteins. Watch out for extra salt and sugar, and stay away from any food that is too small or round.
You can also start to spread out the breast milk and formula feeds as your baby’s schedule begins to revolve more around family meals. However, milk should remain your baby’s main source of calories and nutrition until they reach age one.
Sleep patterns
Another sleep progression is coming. The 8-month sleep regression/progression is timed with a big developmental leap, and might signify some interrupted sleep for you and your little one. Keep your routines for nap time and bedtime consistent and you will both be able to get through the 8-month sleep regression/progression relatively unharmed. Around 9 months of age, parents report that their infant’s sleep is more consistent and life with them feels easier. Phew.
When should I be concerned about my baby’s size?
The growth of your baby should follow a fairly consistent pattern. Weight is not the only metric to determine how your baby is developing. The head circumference, length and developmental milestones also play a part.
Boston Children’s Hospital reports that signs of slow growth may include:
If your baby does not gain weight within the first 14 days of birth
If your baby is not gaining an ounce per day up to three months old
Your baby’s growth suddenly stops if it has been steady.
You can contact your child’s doctor if you are concerned. The doctor will examine the frequency of feedings, the amount consumed at each feed and the number wet and dirty nappies to determine the whole picture.
Weight of babies in the 10th, 11th and 12th months
Every day, your baby becomes more and more their own person. It’s hard for you to believe that your baby was a tiny newborn just a few months ago. They are now showing an increased interest in food, grasping objects and even understanding simple instructions. Your baby’s weight should have tripled by their first birthday. Although their weight gain has slowed compared to the first six months, they still should gain a few pounds each month from months 10 through 12
Average weight at 10 months
A baby boy 10 months old in the 50th per centile weighs approximately 20 pounds, 3 ounces.
A baby girl 10 months old in the 50th per centile weighs 18 pounds 11 ounces (8 kilograms).
Baby Growth & Health Guide for 10-Month-Old Babies
Average weight at 11 months
A baby boy 11 months old in the 50th per centile weighs approximately 20 pounds 12 ounces (9.5 kilograms).
The 50th percentile weight for a 11-month old baby girl is 19 pounds, 4ounces (8.7 kg).
Refer to the 11-month-old Baby Health & Growth Guide
Average weight at 12 months
A baby boy 12 months old in the 50th per centile weighs 9.6 kilograms (21 pounds).
A baby girl aged 12 months in the 50th per centile weighs 19.9 kg (8.9 pounds).
Baby Growth & Health Guide for 12-Month-old Babies
Nutrition and feeding
You can distract your baby while they are breastfeeding or drinking a bottle. If you can, feed your child in a quiet, darkened environment away from distractions. If that doesn’t work, try the opposite: Feed them while wearing your baby, walking, or listening to an audiobook or music. Even though solids have become more important in their lives, breast milk and formula are still vital to their development.
Sleep patterns
Around the 9- to 10-month mark your child may be ready for a shorter nap. This means that they will likely go from taking three naps per day to only two. It’s time to be strategic about wake windows. Make sure that the longest period of wakefulness is in the late afternoon before bedtime. This will help your baby develop a regular sleeping pattern, and allow him to sleep longer at night. It’s worth it to get your child on a sleep schedule.
Motherly’s note on the first year of your baby’s growth
Mama, take stock. You’ve come a long way, mama. We hope you will look back at this first year and reflect on the growth and changes you both experienced. You’ve grown together, from first smiles to your first steps. Remember, if you ever have questions or concerns about your child, you can always contact their pediatrician who will be able to help you decide the next steps.