Baby Growth Percentile Calculator
Enter your baby's weight or length, age, and sex to see the WHO-style percentile band it falls in — and remember the trend matters more than any single point.
Reading the curve, not the number
Percentiles worry new parents more than almost anything, usually needlessly. A baby who is feeding well, has plenty of wet diapers, and follows their own line on the chart is thriving — whether that line sits at the 15th or the 85th. This tool gives you the band; your pediatrician gives you the trend.
Support steady growth with the Baby Feeding Amount Calculator and healthy rest with the Baby Sleep Schedule Planner.
Frequently Asked Questions
What does a growth percentile actually mean?
A percentile compares your baby to a large reference population of the same age and sex. The 50th percentile is the median; a baby at the 30th percentile for weight is heavier than about 30% of babies that age and lighter than the other 70%. It's a ranking, not a score — being at the 20th or the 80th is equally healthy.
Which reference does this use?
It compares your figure against a compact, curated snapshot of the WHO Child Growth Standards — the international reference for weight-for-age and length-for-age in the first years — at a set of reference ages (birth, 1, 2, 3, 6, 9, and 12 months). Your age is snapped to the nearest of those, so treat the band as an approximation of a full growth chart.
Should I worry if my baby is on a low or high percentile?
Usually not. Babies are born to be different sizes, and a consistent low or high percentile is typically just their build. What pediatricians watch is the trend — a baby who tracks steadily along their own curve is doing well. A sudden jump or drop across percentile lines is the thing to flag, not the number itself.
Is this the same as what my pediatrician uses?
It's the same idea, simplified. Your pediatrician plots every visit on a full growth chart, follows the curve over time, and factors in head circumference, feeding, and your baby's history — none of which a single-point estimate can do. Use this to understand the concept and prepare questions, then rely on your provider's chart.
Informational estimate against a simplified reference, not medical advice or a diagnosis. Growth is best judged over time by your pediatrician — consult them about your baby's measurements.