WHO Growth Standards (0-24 Months)

The WHO Child Growth Standards (0-24 months) are the international reference for infant and toddler growth, derived from the WHO Multicentre Growth Reference Study (MGRS) conducted across six countries (Brazil, Ghana, India, Norway, Oman, USA) representing optimal feeding and care conditions. The 0-24 month standards are widely used in pediatric primary care globally.

Each calculator on this page returns a percentile rank against the WHO reference, a z-score, and a visual placement on the percentile chart. Use these for routine well-child visits and growth-trend monitoring.

When to use the WHO 0-24 month standards

The WHO 0-24 standards are the recommended reference for breastfed and formula-fed infants worldwide. WHO and the AAP both endorse WHO for the 0-24 month range; the CDC chart (also on this site) is appropriate from 24 months upward.

Use weight-for-age for general growth-velocity tracking, length-for-age for linear growth, head-circumference-for-age as a developmental screen, and weight-for-length or BMI-for-age to identify underweight or overweight patterns independent of age.

Frequently Asked Questions

Why use WHO instead of CDC for infants?

The WHO standards are derived from a multinational sample of optimally-fed infants under recommended feeding and care; the CDC chart is a U.S.-based reference reflecting actual growth patterns in a population with mixed feeding. The AAP and WHO both recommend using WHO for the 0-24 month range to reduce over-diagnosis of growth failure in breastfed infants.

What does the percentile mean?

A child's percentile rank is the percent of the reference population with smaller (or equal) values at the same age and sex. A 50th percentile is exactly average; 3rd-97th is the band typically reported as 'within normal limits.' Values outside that band warrant clinical interpretation, not automatic concern.

How is the z-score related to the percentile?

Z-score and percentile express the same position in different units — z is the number of standard deviations above or below the median; percentile is the cumulative-probability translation. The growth calcs display both because clinical literature uses both interchangeably.

Why are boy and girl charts separate?

Anthropometric reference data are sex-specific because the underlying growth distributions differ. Plotting a girl on a boy's chart (or vice versa) shifts the percentile interpretation systematically. Every calculator on this page asks for sex and selects the matching reference.