The BMI Calculator for Kids uses the CDC growth chart method to calculate your child's body mass index-for-age percentile. Unlike adult BMI, children's BMI is measured as a percentile against other children of the same age and sex. A healthy percentile is between the 5th and 85th percentile.
What Is Best Bmi Calculator for Kids?
The BMI Calculator for Kids is a specialised tool designed for children and teenagers aged 2 to 19. It calculates child BMI using the same formula as adult BMI (weight/height²), but unlike adult BMI, the result is expressed as a bmi percentile — a comparison against CDC reference data for children of the same age and sex.
Standard adult BMI thresholds (like 25 for overweight) cannot be applied to bmi for kids because children's healthy weight ranges change significantly as they grow. A BMI of 18 is perfectly normal for a 10-year-old but underweight for an adult. The CDC growth chart system resolves this by normalizing each child's BMI against thousands of children of the same age and sex.
According to the CDC, pediatric bmi percentiles are the preferred method for weight status screening in children, and are used by paediatricians, schools, and public health programs across the United States.
How the CDC BMI Calculator for Kids Works
Our cdc bmi calculator for children uses the CDC 2000 growth chart reference data — the most widely validated dataset for child BMI screening. The process works in three steps:
- Your child's height and weight are used to compute their raw BMI (kg/m²)
- That BMI is compared to the CDC's age-and-sex specific reference curves
- A percentile is determined — representing where the child falls relative to peers
The bmi percentile result tells you what percentage of same-age, same-sex children have a lower BMI. A child at the 60th percentile has a higher BMI than 60% of children their age and sex — which is perfectly normal.
BMI Chart for Kids — Percentile Ranges by Age
The bmi chart by age and gender for children uses percentile bands rather than fixed thresholds:
| Percentile | Category | What It Means |
|---|---|---|
| Below 5th | Underweight | May need nutritional evaluation — consult a paediatrician |
| 5th – 84th | Healthy Weight | Normal, healthy range for age and sex |
| 85th – 94th | Overweight | Above healthy range — monitoring recommended |
| 95th or higher | Obese | Significantly above healthy range — consult a paediatrician |
How to Use Best Bmi Calculator for Kids
Enter Your Child's Age
Type in your child's age in whole years (2–19). The calculator uses age-specific CDC reference data, so accuracy here is important.
Enter Height and Weight
Toggle between Imperial (feet/inches and pounds) or Metric (cm and kg). Enter current measurements for the most accurate result.
Read the BMI Percentile Result
Click Calculate Percentile. Your child's BMI number, percentile category, and CDC-based classification appear instantly.
BMI Calculator for Kids vs Adults — Key Differences
Adult BMI uses fixed cut-off values (e.g., BMI ≥ 30 = obese) that apply to all adults aged 20 and over. BMI children screening is fundamentally different:
- Children's healthy BMI changes every year as they grow — there are no fixed adult-style thresholds
- Boys and girls have different BMI-for-age reference curves (the CDC provides separate charts)
- Results are expressed as percentiles, not categories like "overweight" in absolute terms
- A single BMI measurement is less meaningful than tracking trends over multiple years
- Pediatric bmi screening should always be interpreted by a paediatrician in the context of the child's overall growth history
The American Academy of Pediatrics recommends annual BMI screening for all children and adolescents at well-child visits, using age-and-sex standardised percentile charts.
For adult BMI calculators:
BMI Calculator for Kids — Frequently Asked Questions
Our free BMI Calculator for Kids uses the CDC growth chart method to give you an accurate pediatric bmi percentile for children ages 2–19. This child BMI calculator is built on validated CDC reference data and is completely free to use. For adult BMI, visit our main BMI Calculator.