Kid Growth Percentile Calculator
Plot your child's height, weight, and head circumference against WHO and CDC growth charts. See their percentile and get an adult height estimate.
Used for Khamis-Roche adult height prediction (ages 4–17.5 yr) and mid-parental height estimate.
How It Works
A growth percentile tells you how a child compares to a reference population of the same age and sex. A height at the 75th percentile means the child is taller than 75% of children their age. Percentiles between the 5th and 95th are generally considered within the typical range, but trends over time matter more than any single measurement.
Reference Standards
For children under 2 years, this tool uses the WHO 2006 Growth Standards, developed from a multicountry study of children raised in optimal conditions (breastfed, non-smoking households, etc.). Length is measured lying down.
For children 2 years and older, the tool switches to the CDC 2000 Growth Charts, which represent a cross-section of the U.S. population ages 2–20. Height is measured standing.
LMS Method
Percentiles are calculated using the LMS (Lambda-Mu-Sigma) method developed by Cole (1988). Each age has three parameters: L (Box-Cox power transformation to normalize the distribution), M (the median), and S (the coefficient of variation). The Z-score is calculated as:
Z = ((value/M)^L − 1) / (L × S)The percentile is then the area under the standard normal curve to the left of Z.
Adult Height Prediction
The Khamis-Roche method (1994, Pediatrics 94:504–507) predicts adult stature from the child's current height, weight, and mid-parental height, for ages 4–17.5 years. The published standard error of estimate is approximately 2.1 inches (5.3 cm) for boys and 1.7 inches (4.3 cm) for girls.
The mid-parental height formula is a simpler estimate: boys = (mother + father + 13 cm) / 2; girls = (mother + father − 13 cm) / 2; with a typical range of ±8.5 cm.
BMI for Children
Unlike adult BMI, children's BMI is interpreted relative to age and sex. Categories follow CDC guidelines: below the 5th percentile = underweight; 5th–85th = healthy weight; 85th–95th = overweight; 95th and above = obese. BMI is not calculated for children under 2 years.
Data Sources
- WHO 2006 Child Growth Standards: de Onis M, et al. WHO Child Growth Standards. Geneva: WHO Press, 2006.
- CDC 2000 Growth Charts: Kuczmarski RJ, et al. Vital Health Statistics 11(246), 2002.
- Khamis-Roche adult height prediction: Khamis HJ, Roche AF. Pediatrics. 1994;94:504–507. (Erratum: 1995;95:457.)
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Frequently Asked Questions
What does a growth percentile mean?
A growth percentile shows how a child compares to a reference population of the same age and sex. A child at the 75th percentile for height is taller than 75% of children their age. Percentiles between the 5th and 95th are generally within the healthy range.
What is the difference between WHO and CDC growth charts?
WHO 2006 charts are based on children raised under optimal conditions worldwide and are recommended for children under 2 years. CDC 2000 charts represent a cross-section of the US population ages 2–20. This calculator automatically uses WHO under age 2 and CDC from age 2 onward.
Should I be worried if my child is below the 5th percentile?
A single measurement below the 5th percentile may warrant a conversation with your pediatrician, but context matters. A child who has consistently tracked near the 5th percentile is different from one who has dropped from the 50th. Always discuss growth concerns with a healthcare provider.
How accurate is the adult height prediction?
The Khamis-Roche method (used here) has a standard error of about 2.1 inches (5.3 cm) for boys and 1.7 inches (4.3 cm) for girls. It is most accurate between ages 4 and 17.5. The simpler mid-parental height formula has a wider range of ±8.5 cm.
Is BMI interpreted the same way for children as for adults?
No. Adult BMI uses fixed cutoffs (18.5, 25, 30). For children, BMI is age- and sex-specific and expressed as a percentile. Under the 5th percentile is underweight; 5th–85th is healthy weight; 85th–95th is overweight; 95th and above is obese.