What Are WHO Growth Charts?
WHO growth charts come from the World Health Organization Child Growth Standards, released in 2006 after the Multicentre Growth Reference Study. According to CDC training materials summarizing the WHO project, the MGRS followed 8,440 children across Brazil, Ghana, India, Norway, Oman, and the United States between 1997 and 2003. The study was designed to reflect healthy growth under favorable conditions.
That design matters. WHO charts are normative standards, which means they aim to describe how children should grow when health conditions are supportive, smoking exposure is minimized, and breastfeeding is the expected pattern early in life. In practice, that makes WHO growth charts especially important for infants and younger toddlers, and it is why parents often see WHO growth chart 0-2 guidance in U.S. pediatric materials. If that is the age range you need right now, go straight to the baby growth chart calculator or the toddler growth chart page.
What Are CDC Growth Charts?
CDC growth charts are the 2000 revised U.S. growth references. The official CDC data documentation explains that these charts were built from five national survey datasets collected between 1963 and 1994. Because the input comes from nationally representative U.S. samples, the CDC charts describe how children in those datasets actually grew rather than defining an ideal growth target.
That is why CDC charts are usually described as descriptive references rather than normative standards. They are widely used in U.S. clinical practice from age 2 through 20 years for stature, weight, and BMI-for-age. If parents search for the CDC growth chart 2-20 recommendation, this is the core reason: the CDC system provides full childhood and adolescent coverage in the age range where U.S. practice most often uses it. On this site, the most relevant next pages are the child growth chart calculator and the kids BMI percentile calculator.
Why Do Growth Values Differ Between WHO and CDC Charts?
The biggest reason WHO and CDC charts differ is that they were built from different populations for different purposes. WHO charts describe expected growth under healthy conditions, with breastfeeding as a central part of the infant reference. CDC charts describe observed growth in historical U.S. survey data, where feeding patterns were more mixed. This difference is especially visible in infant weight percentiles.
In plain language, a breastfed baby can look lower on a CDC weight chart and completely ordinary on a WHO chart at the same age. That does not mean one chart is right and the other is wrong. It means the reference populations differ. This is also why CDC training materials and routine AAP pediatric guidance favor WHO charts for children under 24 months in routine U.S. use.
Which Chart Should I Use for My Child?
The chart selection guide is simpler than most families expect. The main decision is the child's age, then whether special circumstances like prematurity apply. If you want the short version, the tree below covers most routine cases.
Is your child younger than 24 months?
→ Use WHO growth charts for routine infant and early toddler assessment.
Is your child age 2 or older?
→ Use CDC growth charts for height, weight, and BMI-for-age through age 20.
Was your child born premature?
→ Use corrected age during early follow-up, often through the first 2 to 3 years depending on clinical practice.
Are you outside the United States?
→ Many countries keep using WHO standards longer, especially through age 5, even though U.S. practice often switches at age 2.
For most U.S. families, the simplest rule is WHO under 24 months and CDC from age 2 onward. If the child was born premature, corrected age can matter during early follow-up. AAP HealthyChildren guidance notes that corrected age may be used through the first 2 years and, in some cases, through the first 3 years, so percentile interpretation should stay consistent with the clinician's method. Families can then choose the age-matched page for actual screening: baby growth chart, toddler growth chart, or child growth chart.
What Happens at Age 2 — Why Charts Switch from WHO to CDC
Age 2 is not just an arbitrary rule. It is also where measurement technique changes. Younger children are usually measured lying down for recumbent length, while older children are measured standing for stature. That shift alone can change the plotted value slightly because recumbent length is often about 1 to 2 cm greater than standing height.
CDC guidance and common AAP pediatric practice use this age-2 transition to move children from WHO infant-style assessment to CDC stature, weight, and BMI-for-age references. On this site, the calculator defaults to that switch automatically, while comparison pages can still pin WHO or CDC manually when a clinician wants a fixed reference during review. In practical terms, this is the handoff between the infant calculator and the older-child tools such as the BMI calculator for kids.
How the Same Child Can Have Different Percentiles on WHO vs CDC
The examples below show why the same child can have different WHO and CDC percentiles without any change in the child's body. The only thing changing is the reference system. This is not a question of which chart is more accurate in the abstract. It is a question of which chart is more appropriate for the child's age and clinical context.
Example: 12-month-old boy, weight 9.5 kg, length 75 cm
Weight and length rows use this site's local WHO and CDC datasets. The weight-for-length row is an illustrative chart-based comparison.
| Metric | WHO percentile | CDC percentile | Why it differs |
|---|
| Weight percentile | P44.4 | P22.8 | CDC infant weight references run heavier, so the same breastfed baby often looks lower on CDC weight-for-age. |
| Length percentile | P37.6 | P42.9 | Length percentiles often differ less than weight percentiles in infancy. |
| Weight-for-length percentile | P55 | P48 | Illustrative chart-based comparison: WHO weight-for-length references are generally friendlier to healthy breastfed infant body shape than older CDC references. |
Example: 24-month-old girl, weight 12.0 kg, height 86 cm
Includes BMI 16.2 kg/m². WHO BMI uses the official WHO girls 24-month BMI-for-age reference row; CDC BMI uses this site's local dataset.
| Metric | WHO percentile | CDC percentile | Why it differs |
|---|
| Weight percentile | P63.9 | P48.3 | By age 2 the gap often narrows, but WHO and CDC can still place the same child on different channels. |
| Height percentile | P44.9 | P61.6 | At age 2 the switch from recumbent length to standing stature also changes the comparison. |
| BMI percentile | P65.3 | P44.3 | BMI differences can still be meaningful near the age-2 transition because the reference systems are built differently. |
Percentile values are approximate and shown for illustration. Exact values depend on exact age in months, measurement method, and the chart standard used.
How This Calculator Handles WHO and CDC Standards
The calculator uses WHO standards automatically for children younger than 24 months and switches to CDC standards from 24 months onward. BMI-for-age is shown with CDC references once age allows. The results area also tells the user which standard was applied, so the comparison is visible instead of hidden.
On pages that support comparison mode, you can keep the automatic WHO-to-CDC switch or manually pin one standard while checking how the same measurements look under a different reference. For early prematurity or special clinical follow-up, clinician guidance still matters because corrected age and specialty-specific workflows can affect interpretation.