Baby Weight and Length Chart by Month (0–24 Months): WHO Averages for Boys and Girls
Median weight and length for each month from birth to age 2, with the normal 5th-to-95th percentile range, how to read percentiles, and when growth is worth a pediatrician's attention.
What parents should know
- Percentiles compare your baby with healthy breastfed babies in the WHO study; 50th is the middle, not the goal.
- Growth is fastest in the first 6 months and slows in the second year.
- One measurement means little; the trend across visits tells the story.
- Crossing two major percentile lines up or down is a reason to ask your pediatrician.
- Premature babies are plotted by corrected age.
Baby weight and length chart by month
| Age | Boys weight: median (5th–95th) | Boys length (median) | Girls weight: median (5th–95th) | Girls length (median) |
|---|---|---|---|---|
| Birth | 7.4 lb (5.7–9.3) | 19.6 in | 7.1 lb (5.6–8.9) | 19.3 in |
| 1 months | 9.9 lb (7.9–12.2) | 21.5 in | 9.2 lb (7.3–11.5) | 21.1 in |
| 2 months | 12.3 lb (10.0–15.0) | 23.0 in | 11.3 lb (9.1–14.0) | 22.5 in |
| 3 months | 14.1 lb (11.6–17.0) | 24.2 in | 12.9 lb (10.5–15.8) | 23.5 in |
| 4 months | 15.4 lb (12.8–18.5) | 25.2 in | 14.2 lb (11.5–17.4) | 24.4 in |
| 5 months | 16.6 lb (13.8–19.8) | 25.9 in | 15.2 lb (12.4–18.6) | 25.2 in |
| 6 months | 17.5 lb (14.6–20.9) | 26.6 in | 16.1 lb (13.2–19.7) | 25.9 in |
| 7 months | 18.3 lb (15.3–21.8) | 27.2 in | 16.8 lb (13.8–20.6) | 26.5 in |
| 8 months | 19.0 lb (15.9–22.7) | 27.8 in | 17.5 lb (14.4–21.5) | 27.1 in |
| 9 months | 19.6 lb (16.4–23.4) | 28.3 in | 18.1 lb (14.9–22.2) | 27.6 in |
| 10 months | 20.2 lb (16.9–24.1) | 28.9 in | 18.7 lb (15.3–22.9) | 28.1 in |
| 11 months | 20.8 lb (17.3–24.8) | 29.3 in | 19.2 lb (15.8–23.6) | 28.6 in |
| 12 months | 21.3 lb (17.8–25.4) | 29.8 in | 19.7 lb (16.2–24.2) | 29.1 in |
| 15 months | 22.7 lb (19.0–27.2) | 31.2 in | 21.2 lb (17.4–26.0) | 30.5 in |
| 18 months | 24.1 lb (20.1–28.9) | 32.4 in | 22.6 lb (18.5–27.8) | 31.8 in |
| 21 months | 25.5 lb (21.2–30.6) | 33.5 in | 23.9 lb (19.6–29.5) | 32.9 in |
| 24 months | 26.8 lb (22.2–32.3) | 34.6 in | 25.3 lb (20.8–31.2) | 34.0 in |
How to read percentiles
If your baby is at the 30th percentile for weight, 30 out of 100 healthy babies of the same age and sex weigh less and 70 weigh more. Small parents often have small babies, and tall parents tall ones. The WHO standards describe how healthy children grow under good conditions, based on children raised mostly on breast milk (WHO), which is why the CDC recommends them for babies under 2 (CDC).
Weight, length and head size are each plotted separately, and doctors also look at weight-for-length. A baby whose weight and length percentiles are very different may need a closer look even if each is in the normal range.
How fast babies grow
- From the table, the median boy gains about 10 lb in the first 6 months but only about 4 lb from 6 to 12 months.
- The median baby grows roughly 10 inches in the first year and about 5 inches in the second.
- Many newborns lose some weight in the first days and regain it over the next couple of weeks; your pediatrician checks this at early visits.
- Growth spurts can bring a few days of extra hunger; responsive feeding lets your baby lead (AAP).
What affects your baby's growth
- Genetics and parents' size.
- Feeding: breastfed and formula-fed babies can follow slightly different patterns; see our formula amounts by age chart.
- Prematurity: use corrected age until about age 2.
- Illness: a stomach bug or ear infection can pause weight gain for a week or two.
- Starting solids around 6 months adds calories and iron (AAP).
When to talk to your pediatrician
- Weight drops across two or more major percentile lines, or stops rising over several visits.
- Fewer wet diapers, feeding refusal or ongoing vomiting.
- Weight is far above length, or rising much faster than length.
- Head size is growing much faster or slower than expected.
- Your baby is losing skills or seems unusually sleepy or weak.
Frequently asked questions
What is the average weight of a 6-month-old?
About 17.5 lb for boys and 16.1 lb for girls (WHO median). Healthy babies range from about 13 to 21 lb.
How much should a 1-year-old weigh?
The WHO median is about 21.3 lb for boys and 19.7 lb for girls, with a normal range of roughly 16 to 25 lb.
Is the 10th percentile bad?
No. Any percentile from about the 5th to 95th can be normal if your baby follows a steady curve.
Which growth chart should I use for my baby?
The CDC recommends the WHO growth standards for children under 2 and CDC charts from age 2.
Keep reading
Sources
This guide was checked against the current guidance below. Medical and safety recommendations can change; use the linked source and your child's clinician for decisions specific to your family.
- WHO: Child growth standards
- CDC: WHO growth standards are recommended for use in the US for infants and children 0 to 2 years
- CDC/NCHS: WHO weight-for-age and length-for-age percentile data files
- HealthyChildren.org (AAP): Amount and schedule of formula feedings
- HealthyChildren.org (AAP): Starting solid foods