Baby growth percentile calculator
See where your baby's weight, length, and head size fall on the WHO growth charts that pediatricians in the US use from birth to age 2.
For babies born 3 or more weeks early, percentiles use adjusted age until age 2.
A percentile compares your baby with healthy babies of the same age and sex. The 50th is the middle, not a target: healthy babies grow along every percentile. What matters most is that your baby keeps following their own curve over time. This calculator is for information only. Your pediatrician will look at the full picture.
Sources
- WHO Child Growth Standards (World Health Organization). Percentiles use the WHO's published LMS tables for weight, length, and head circumference.
- WHO growth charts for children under 2 (Centers for Disease Control and Prevention), which recommends the WHO charts for US children from birth to age 2.
How to read a percentile
If your baby's weight is at the 30th percentile, about 30 out of 100 babies of the same age and sex weigh less, and about 70 weigh more. Small babies and big babies are both normal. Doctors pay attention when a baby is below the 2nd or above the 98th percentile on the WHO charts, or when their percentile drops or climbs a lot between visits.
Common questions
What does my baby's growth percentile mean?
It compares your baby with healthy babies of the same age and sex. At the 40th percentile for weight, about 40 out of 100 babies weigh less and 60 weigh more. Every percentile can be healthy.
Which growth chart does this calculator use?
The World Health Organization growth standards, which the CDC and the American Academy of Pediatrics recommend for US children from birth to age 2.
When should I worry about my baby's percentile?
Doctors look more closely when a baby is below the 2nd or above the 98th percentile on the WHO charts, or when a baby's percentile changes a lot between visits. A single number rarely tells the whole story, so ask your pediatrician.
Does this work for premature babies?
Enter how many weeks early your baby was born and the calculator uses adjusted age, as doctors usually do until age 2. Before reaching their due date, babies born early are tracked on special preterm charts.
Track the curve, not one number.
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