Baby Weight-for-Age Percentile Calculator

Any percentile from the 3rd to the 97th is considered within the normal range. There is no single 'ideal' percentile — the goal is consistent growth along your baby's curve over time, not a specific number.

No. The 50th percentile simply means your baby weighs the same as the median baby of that age and sex. A baby consistently at the 20th or 80th percentile is perfectly healthy as long as they track their own curve. Percentile shifts — especially crossing two major lines — are what concern pediatricians.

Some percentile variation is normal, especially in the first few weeks. However, a drop of two or more major percentile lines (e.g., 75th → 25th) over a few months warrants a conversation with your pediatrician, as it may indicate a feeding issue, illness, or other growth concern.

American Academy of Pediatrics (AAP) recommends well-child visits at 3–5 days (for newborns), 1 month, 2 months, 4 months, 6 months, 9 months, 12 months, 15 months, 18 months, 24 months — with weight taken at each visit.

Below the 3rd percentile is sometimes called 'low weight for age.' It does not automatically indicate a problem — some families are simply smaller-framed. However, your pediatrician will evaluate whether the weight is appropriate for your baby's length, history, and trajectory, and may investigate feeding, digestion, or medical causes.

WHO charts (used here) are based on children raised in healthy conditions across 6 countries and represent how children should grow under optimal conditions. CDC charts describe how a typical US child grew (1970s–1990s data). AAP recommends WHO charts for children under 2 years and CDC charts for ages 2–20. This calculator uses WHO data throughout.