Tools · Baby
Baby Growth Percentile Calculator (WHO Standards)
Free baby growth percentile calculator using the official WHO Child Growth Standards. Enter your baby's age, sex, and weight, length, or head circumference to see their percentile.
Enter your baby's measurement to see their percentile.
Based on the official WHO Child Growth Standards (0–24 months). A single measurement is a snapshot, not a diagnosis — always discuss growth trends with your pediatrician.
How Percentiles Are Calculated
This calculator uses the WHO Child Growth Standards' LMS method: for every age in months, WHO publishes three parameters (L, M, and S) that describe the exact statistical distribution of that measurement in a healthy reference population. Your baby's raw measurement is converted into a z-score — a measure of how many standard deviations it is from the median — and the z-score is then converted into a percentile using the standard normal distribution.
This is the same underlying method pediatricians and growth-chart software use — not a simplified approximation. Because it is based on the raw L/M/S values published by WHO for each individual month, the percentile shown here matches what you would get by plotting the same measurement on an official WHO growth chart.
Frequently Asked Questions
What growth standard does this calculator use?
This calculator uses the official WHO (World Health Organization) Child Growth Standards, the internationally recognized reference for how healthy children grow when given optimal nutrition and care, regardless of ethnicity or country. It covers weight-for-age, length-for-age, and head-circumference-for-age from birth to 24 months, separately for boys and girls.
What does a percentile actually mean?
A percentile shows where your baby's measurement falls compared to a reference population of babies the same age and sex. A weight at the 40th percentile means about 40% of babies that age weigh less and about 60% weigh more. Being at the 20th or the 80th percentile are both entirely normal — percentile is not a grade, it is a position.
Is a lower or higher percentile better?
Neither. A healthy baby can track anywhere from the 3rd to the 97th percentile. What matters most to pediatricians is a consistent growth pattern over time (a baby following roughly the same percentile band across multiple checkups) rather than the single number on any one day. A sudden, large jump up or down across percentile lines is more worth discussing than the absolute percentile itself.
My baby is outside the 0–24 month range or over 5th/under 95th — what should I do?
This tool only covers 0–24 months. For older children, or if your baby's percentile is very low (under about the 3rd) or very high (over about the 97th), or has shifted a lot since the last checkup, bring it up with your pediatrician — they have your baby's full growth history and can tell you whether it needs attention.
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