WHO growth charts are the international standard for tracking a child’s physical development from birth through age 19. They show how your child’s weight, height, and body composition compare to a large population of healthy children raised under optimal conditions. Most pediatricians in the U.S. and around the world use these charts at every well-child visit to spot potential growth concerns early.
What the WHO Charts Actually Measure
For children under five, the WHO charts track several key measurements: length or height for age, weight for age, and body mass index (BMI) for age. For older children and adolescents aged 5 to 19, the charts include BMI for age and height for age. Weight for age is only charted up to age 10 in this older group because weight alone becomes less meaningful as children enter puberty and gain height at very different rates.
Each measurement is plotted against your child’s age and sex. The result is a dot on a curve that shows where your child falls relative to other healthy children of the same age and sex.
How the Charts Were Built
The WHO growth standards for children under five came out of a large international study across six countries. What makes these charts different from older references is that the children included were specifically selected to represent healthy growth. Infants were excluded if their mothers smoked during pregnancy or while breastfeeding, if they were breastfed for less than 12 months, or if they started solid foods before four months of age.
This matters because the WHO charts don’t just describe how children happened to grow in a particular country at a particular time. They represent how children should grow when nutrition and health conditions are good. The breastfed infant is the baseline model for normal growth, which was a deliberate choice made by the World Health Assembly in 1994.
Percentiles and Z-Scores Explained
When your pediatrician says your child is at the 50th percentile for weight, it means 50% of healthy children the same age weigh less and 50% weigh more. The 50th percentile is the median, and it corresponds to a z-score of zero. A z-score simply tells you how far above or below the median your child’s measurement falls, measured in standard deviations. The 97th percentile, for example, equals a z-score of about +1.88.
Being at a high or low percentile is not automatically a problem. A child who has tracked along the 15th percentile since infancy is likely perfectly healthy. What matters more is the pattern over time. Consistent growth along a curve is reassuring. A sudden jump or drop is what gets attention.
When Percentile Changes Are Normal
During the first two to three years of life, it is completely normal for children to shift one or two percentile lines on the chart. Many babies are born larger or smaller than their genetic potential and gradually settle toward where they’re meant to be. A shift toward the 50th percentile during this period is generally considered healthy.
After that early adjustment period, a child’s growth typically follows the same curve consistently. A sharp incline, a flat line, or a noticeable decline from an established pattern can signal a growth disturbance. Clinicians look for shifts that cross two major percentile lines, and they often investigate before a child reaches that threshold. Unexpected downward movement may point to failure to thrive, while unexpected upward movement could indicate developing overweight or obesity. During puberty, some variability returns because children enter growth spurts at different ages.
WHO Charts vs. CDC Charts
In the United States, the CDC recommends using WHO growth standards for all children from birth to age 2. After age 2, the CDC’s own growth charts are typically used. The key difference is philosophical: WHO charts are a prescriptive standard showing how healthy children should grow, while CDC charts are a descriptive reference showing how American children actually grew during a specific time period. The CDC charts don’t imply that the growth patterns they capture are healthy.
There’s also a practical difference in how the percentile lines are spaced. The WHO charts use the 3rd, 15th, 50th, 85th, and 97th percentile lines, while the CDC charts use the 10th, 25th, 50th, 75th, and 90th. Because the inner curves on the WHO charts are farther apart, a child would need to gain or lose more weight before crossing two lines. This means the WHO charts are slightly less sensitive to small fluctuations but better at flagging truly significant changes.
Cutoffs for Underweight and Overweight
The WHO uses z-score thresholds to classify nutritional status in children aged 5 to 19. A BMI-for-age above +1 standard deviation is considered overweight, which corresponds roughly to a BMI of 25 at age 19. Above +2 standard deviations is classified as obesity, equivalent to a BMI of 30 at age 19. On the other end, below -2 standard deviations is classified as thinness, and below -3 is severe thinness.
For younger children under five, similar z-score cutoffs apply to weight-for-height and other indicators to identify wasting (too thin for height) and stunting (too short for age). These definitions are used globally to track childhood malnutrition at population levels, but they also help pediatricians evaluate individual children.
One nuance worth understanding: BMI is more strongly related to weight than to height. A child at the 97th percentile for both weight and height doesn’t necessarily have a normal BMI. Research published in JAMA Pediatrics found that such a child would still have a predicted BMI around the 88th percentile, above the overweight threshold. Being tall doesn’t cancel out being heavy when it comes to BMI-for-age.
Using the Charts for Preterm Infants
If your baby was born prematurely, growth should be plotted using corrected age rather than chronological age. Corrected age adjusts for how early the baby arrived by subtracting the weeks of prematurity from the actual age. A baby born at 34 weeks who is now 4 months old would be plotted as a 2.5-month-old on the WHO chart.
The standard practice has been to use corrected age until a child turns 2, but recent evidence suggests this may not be long enough. A 2025 study in the Journal of Perinatology found that for extremely and very preterm children, age correction should continue through 36 months of corrected age. Without this adjustment, these children can be misclassified as underweight or short when their growth is actually on track for their developmental stage.
How to Access WHO Growth Charts
The WHO provides several free tools for plotting and calculating growth data. The WHO Anthro software, available for Windows, includes an anthropometric calculator for generating z-scores and percentiles, an individual assessment module useful in clinical settings, and a nutritional survey module for population-level analysis. There is also an online version called the WHO Anthro Survey Analyser, developed jointly with UNICEF.
For most parents, you won’t need to use these tools yourself. Your child’s pediatrician plots growth at every visit, and most electronic health record systems do it automatically. But if you want to check the charts at home, the WHO website hosts downloadable PDFs of every chart by age, sex, and measurement type. You can find the under-5 standards and the 5-to-19 reference charts as separate sets, each with their own tables and curves.