Child Growth Percentile Calculator

What Growth Percentiles Mean

A growth percentile tells you how your child’s height or weight compares to other children of the same age and sex. A child at the 60th percentile for height is taller than 60% of children the same age and sex, and shorter than 40%. Percentiles are not grades. There is no good or bad percentile, only your child’s position relative to their peers.

Healthy children come in all sizes. A child consistently at the 10th percentile for height is almost certainly healthy if their growth curve is consistent. It is the trend over time that matters most, not any single measurement.

The CDC vs. WHO Growth Charts

Two major growth chart systems are used for children:

• WHO Growth Standards (2006): Used for children ages 0–2. Based on healthy children from Brazil, Ghana, India, Norway, Oman, and the United States raised in optimal conditions (breastfed, non-smoking households, etc.). Represents how children should grow under ideal conditions. For a baby, use the Infant Growth Percentile Tracker.

• CDC Growth Charts (2000): Used for children ages 2–20 in the United States. Based on a nationally representative sample of U.S. children from 1963–1994. Represents how children did grow, making it a descriptive (rather than prescriptive) reference.

This calculator uses the CDC reference for ages 2–20.

The LMS Method

CDC growth charts use the LMS statistical method. Each age-sex group has three parameters:

• L (Box-Cox power): Adjusts for skewness in the distribution
• M (Median): The 50th percentile value
• S (Coefficient of variation): The spread of the distribution

The z-score is ((measurement ÷ M)^L − 1) ÷ (L × S), and the z-score is then converted to a percentile using the standard normal distribution.

This calculator uses the CDC’s own L, M and S values, taken every six months from 2 to 20 years with a straight line in between. That stays within 0.04 of a z-score of the full half-month table at every age, which is well under one percentile point near the middle of the chart.

Why Genetics Dominates Height

Genetics account for roughly 80% of the variation in adult height. The rest is environmental: nutrition, sleep, illness history. A simple estimate of a child’s adult height is the “mid-parental height” method: for boys, (father’s height + mother’s height + 5 inches) / 2. For girls, (father’s height − 5 inches + mother’s height) / 2. About 4 inches (10 cm) either side of that figure covers most children.

BMI-for-Age: Different From Adult BMI

The BMI cutoffs used for adults (18.5, 25, 30) do not apply to children. For children, BMI is plotted on a growth chart to produce a BMI-for-age percentile:

• Under 5th percentile: Underweight
• 5th to under 85th percentile: Healthy weight
• 85th to under 95th percentile: Overweight
• 95th percentile or above: Obesity

Above the 95th percentile, the CDC’s 2022 extended charts measure BMI as a percentage of the 95th percentile instead, because the old curves bunch together up there and stop telling children apart. 120% of the 95th or more is severe obesity (class 2), and 140% or more is class 3. The American Academy of Pediatrics 2023 guideline uses the same classes. This page reports that percentage rather than a percentile above 95.

These cutoffs are sex-and-age-specific because children’s normal BMI range changes significantly as they grow. An 8-year-old and a 15-year-old girl have different healthy BMI ranges even if they are the same height and weight.

When to Consult a Pediatrician

Consult a pediatrician if:

• Your child’s percentile changes significantly between visits (e.g., drops from 60th to 20th)
• Your child is consistently below the 3rd percentile or above the 97th
• Growth appears to have plateaued or stopped unexpectedly
• Your child appears much shorter or taller than both parents would predict