Baby percentile calculator (WHO)
This calculator estimates your baby’s weight and height percentiles based on the World Health Organization (WHO) child growth standards, valid from 0 to 60 months. A percentile shows the percentage of healthy babies of the same age and sex who weigh or measure less than yours: for example, a weight percentile of 60 means 60% of babies weigh less. Enter the sex, the age (by date of birth or directly in months), the weight and the height to see both percentiles and their interpretation.
Weight percentile
Height percentile
Age in months
Indicative result based on the WHO growth standards (0–60 months). It does not replace your pediatrician: what matters is the baby’s trend over time, not a single number. A low or high percentile does not by itself indicate a problem.
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How it works
For each sex and each month of age, the WHO publishes three parameters (L, M and S) that describe the distribution of weight and height in healthy babies. From them, your baby’s Z-score is computed with the formula Z = ((X/M)^L − 1) / (L × S), where X is the measured weight or height. That Z-score is converted to a percentile using the normal distribution. The 50th percentile is the median (Z = 0); the usual range runs from the 3rd to the 97th percentile. The calculator interpolates between months for in-between ages. What matters is not a single value but the growth curve over time.
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Preguntas frecuentes
- What is a growth percentile?
- It is a way to compare your baby’s weight or height with those of thousands of healthy babies of the same age and sex. A weight percentile of 70 means that out of every 100 babies, 70 weigh less than yours and 30 weigh more. It is not a grade or a ranking: it simply shows where your baby sits within the normal range of variation.
- Which percentile is normal?
- The WHO considers the range from the 3rd to the 97th percentile to be normal. A baby at the 10th percentile can be just as healthy as one at the 90th: both are within what is expected. What matters is that the baby follows its own curve over time, rather than the exact number on a given day.
- My baby is at a low percentile, should I worry?
- Not necessarily. Many healthy babies stay at low percentiles consistently. What the pediatrician watches is the trend: if the baby had been growing along its curve and suddenly drops several percentiles, it is worth checking. A single low value on its own is rarely cause for alarm.
- Do these data apply to premature babies?
- The WHO standards are for babies born at term. For premature babies, the pediatrician usually uses corrected age (subtracting the weeks born early) during the first years. Always consult a professional in these cases.
- Where does the data come from?
- From the WHO Child Growth Standards (2006), an international study of healthy, breastfed babies raised in optimal conditions. They are the reference standard used in most countries for children aged 0 to 5.