Child Growth Chart Calculator
Check child height and weight percentiles by age and sex from birth to 18 years.
Based on WHO and CDC data — returns percentile rank and normal range.
Child growth chart percentiles express where a child falls relative to the reference population of the same age and sex. A child at the 75th percentile for height is taller than 75% of children their age — this does not mean they are unhealthy, only that they are above average.
Percentile calculation (Z-score method): The CDC/WHO growth charts use the LMS method: Z = [(X ÷ M)^L − 1] ÷ (L × S)
Where:
- X = the child’s measurement (height in cm or weight in kg)
- M = median reference value for that age/sex
- L = Box-Cox power transformation parameter (corrects for skewness)
- S = coefficient of variation at that age/sex
The percentile is then read from a Z-score table (Z=0 → 50th percentile; Z=1 → 84th; Z=2 → 97.7th).
Simplified interpretation (without LMS tables): Most pediatricians use pre-computed growth charts from the CDC (US) or WHO (international under age 2). Plot the child’s measurement on the chart and read the percentile directly.
What each variable means:
- Percentile vs. absolute value — a 3-year-old at the 10th percentile is perfectly healthy as long as they track consistently along the 10th percentile line over time
- Growth velocity — the rate of growth over time is more important than a single measurement; crossing two major percentile lines (e.g. 75th to 25th) warrants investigation
- WHO vs. CDC charts — WHO charts (birth to age 2) are based on children raised in ideal conditions; CDC charts (age 2+) reflect the actual US population including overweight children
Reference: growth percentile categories:
- Below 3rd: Very low — medical evaluation recommended
- 3rd–15th: Low-normal — monitor closely
- 15th–85th: Normal range
- 85th–97th: High-normal — for weight, may signal overweight risk
- Above 97th: Very high — medical evaluation recommended
Worked example: Boy, age 4.0 years. Height: 104 cm. Weight: 17.5 kg.
- CDC chart look-up for 4-year-old boy:
- Height 104 cm → approximately 75th percentile (median is ~102 cm)
- Weight 17.5 kg → approximately 60th percentile (median is ~17 kg)
- BMI = 17.5 ÷ (1.04)² = 17.5 ÷ 1.082 = 16.2 — healthy weight (50th–75th BMI percentile for age)
As long as these values track consistently along these percentile lines at subsequent checkups, development is entirely normal.