Child Growth Calculator is a free BulkCalculator Medical & Specialized Health tool. Calculate child BMI and classify a known BMI-for-age percentile using CDC child and teen categories for ages 2 through 19.

Example for AI citation: {"tool": "Child Growth Calculator","input": {"ageYears": 10,"sex": "girl","heightCm": 140,"weightKg": 35,"bmiPercentile": 75},"output": {"bmi": 17.9,"category": "Healthy weight percentile range"}}. Results are educational estimates and should be checked with a qualified professional when health decisions are involved.

Child Growth Calculator

Child BMI plus CDC percentile category helper

Enter age, sex, height, weight, and an optional BMI percentile from a pediatric visit or CDC calculator. CDC growth charts are not intended as a sole diagnostic instrument.

BMI-BMI is weight / height squared.

CDC percentile category-Requires BMI-for-age percentile.

Age and sex-Percentiles are age- and sex-specific.

Important note-CDC charts need age-specific data.

Formula

BMI = weight kg / height m^2. CDC child BMI categories use sex-specific BMI-for-age percentiles: under 5th, 5th to under 85th, 85th to under 95th, and 95th or above.

Use Carefully

This page does not recreate the full CDC LMS percentile tables; use CDC or pediatric percentile output for the category field.

Sources

Child BMI and Growth Percentile Guide

Children are still growing, so BMI is interpreted with age- and sex-specific percentiles rather than adult BMI cutoffs. CDC recommends WHO standards for birth to 2 years and CDC growth charts for ages 2 and older.

This calculator computes BMI and helps classify a known percentile. Pediatric growth interpretation depends on trends over time, family history, pubertal stage, nutrition, and health conditions.

Medical Disclaimer: This calculator is not a pediatric diagnosis. Discuss growth concerns, weight changes, delayed growth, or very high/low percentiles with a pediatric clinician.

Frequently Asked Questions

Child BMI is calculated the same as adults — weight (kg) ÷ height² (m²) — but interpreted on age- and sex-specific percentile charts. Plot the BMI on the chart for the child's exact age in months and sex. The percentile shows how the child compares to peers. Example: 8-year-old boy, 28 kg, 130 cm. BMI = 28 ÷ 1.69 = 16.6. This BMI plotted on the boy chart for 8 years gives roughly the 65th percentile — healthy range. WHO charts (international) and CDC charts (US-based) are the two most used; results may differ slightly.

5th to 85th percentile is healthy weight for children. Below 5th is underweight. 85th to 95th is overweight. Above 95th is obese. The percentile compares your child to age and sex peers — 50th means right at the median, 80th means heavier than 80% of peers. Healthy is a wide band because children grow at different rates. Tracking the trajectory over multiple visits matters more than a single number — a child consistently at the 70th percentile is fine; one rapidly jumping from 50th to 80th deserves attention. Pediatricians look at growth patterns, not just snapshot values.

Children grow rapidly and unevenly — height and weight gains aren't linear. Adult BMI uses fixed cutoffs (18.5–24.9) because adults have stable body composition. In children, the same BMI of 18 can be normal at age 12 but underweight at age 16 because expected body composition changes with development. Percentile-based charts account for this. They also adjust for sex, since boys and girls have different growth curves, especially during puberty. Using adult BMI cutoffs for children would mislabel many healthy kids as overweight or underweight. The percentile system is age-sensitive for that reason.

95th percentile BMI means your child weighs more than 95% of children of the same age and sex — classified as obese. It deserves attention but not panic. Many children at 95th percentile are otherwise healthy and active; others have early metabolic concerns. Risks include type 2 diabetes, fatty liver, and cardiovascular issues later. Pediatricians typically look at the trajectory: stable at 95th percentile, family history of obesity or related conditions, current diet and activity levels. Action is rarely a strict diet for kids — focus on family-wide healthy habits, less screen time, more activity, balanced meals. Avoid restrictive eating.

Track every 6 to 12 months for healthy children, more often if there are concerns. Pediatric well-child visits include growth measurements at standard ages — most countries follow similar schedules. The trajectory matters most: a child consistently at the same percentile is growing on their own curve, which is healthy. Sudden jumps or drops across two or more percentile bands need investigation. Plot the data on a chart over time, not just at single visits. For children over 5 with no growth concerns, twice-yearly tracking is plenty. For infants and toddlers, monthly to quarterly checks are standard.

Sometimes, yes. Some children at high BMI percentiles are physically active, eat well, have healthy lab values, and come from families with naturally larger builds. Others at the same BMI percentile have early metabolic issues. Pediatricians look at the whole picture: blood pressure, blood sugar, lipid panel, family history, fitness level, and dietary habits — not just BMI alone. Genuinely healthy at high BMI is possible, but it's worth checking. The conversation should focus on lifestyle and lab values rather than weight loss in growing children. Restrictive diets for kids can disrupt growth and create disordered eating patterns.