WHO Growth Chart Calculator (0–24 Months)
Infant-focused WHO Child Growth Standards calculator for ages 0–24 months. Enter age in years (e.g. 0.5 = 6 months), sex, length, and weight for z-scores and percentiles.
For ages up to 60 months use the full WHO calculator. For preterm infants use Fenton preterm growth. Browse all tools on the growth calculators hub.
How to interpret WHO infant z-scores and percentiles
A z-score is the number of standard deviations a measurement sits from the WHO median for that age and sex. A z-score of 0 is the 50th percentile. Values near −2 or +2 are about the 2nd and 98th percentiles and usually prompt a closer clinical look, not an automatic diagnosis.
For infants born preterm, enter weeks born early to apply corrected age when comparing to term WHO standards after discharge. In the NICU, use Fenton preterm growth charts plotted by postmenstrual age instead of WHO until your unit transitions to corrected-age plotting.
Trend matters more than one visit. Crossing two major percentile lines, disproportionate weight vs length, or measurements that do not match the clinical picture should be checked against serial data, nutrition, and measurement technique (recumbent length vs standing height after ~24 months).
WHO vs CDC for infants
AAP guidance commonly uses WHO Child Growth Standards from birth through 24 months and CDC 2000 charts from age 2 to 20 years. WHO describes how healthy breastfed infants grow under standard conditions; CDC describes U.S. survey populations. For U.S. infant visits 0–36 months you may also use the CDC infant growth calculator.
Sources and Reference Basis
This calculator uses WHO Child Growth Standards LMS parameters for infants 0–24 months. Use for bedside screening and documentation; interpret with serial measurements and local growth policy.
- WHO Child Growth Standards Reference basis for infant weight, length, BMI, and head circumference z-scores.
- CDC Growth Charts U.S. infant and child charts; see our CDC infant calculator for 0–36 months.
- Fenton 2013 preterm growth Preferred reference for in-NICU preterm infants by postmenstrual age.
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Frequently Asked Questions
Which growth standards does this WHO infant calculator use?
WHO Child Growth Standards for ages 0–24 months, including weight-for-age, length/height-for-age, BMI-for-age, and optional head circumference.
How do I enter age for a 6-month-old?
Enter age in years: 0.5 for 6 months, 1.0 for 12 months, 1.5 for 18 months.
Should I use corrected age for a preterm infant?
After discharge, many clinicians use corrected age (subtract weeks born early) when plotting against term WHO charts. Enter weeks born early in the optional field, or use Fenton charts in the NICU.
When should I switch to CDC charts?
AAP guidance commonly uses WHO from birth to 24 months and CDC from 2 to 20 years. Use the CDC growth chart calculator for older children.