Child and Teen BMI Calculator
Calculates BMI, BMI-for-age percentile, and screening categories for children and teens ages 2–19 using CDC growth chart LMS reference data (screening only; not a diagnosis).
This calculator is commonly searched as a CDC child and teen BMI calculator, CDC child BMI calculator, CDC pediatric BMI calculator, or child BMI calculator CDC (BMI-for-age percentile, ages 2–19).
Quick answer (what this calculator does)
Child BMI is calculated from height and weight, then interpreted using a CDC BMI-for-age percentile that depends on age (in months) and sex. This tool estimates BMI, percentile, category, % of the 95th percentile, and a healthy weight range at the same height.
- Age in months (small differences can change percentile)
- Accurate height (errors strongly affect BMI)
- Sex (CDC reference curves differ)
Interpretation: percentiles compare to same-age, same-sex peers (CDC reference).
Disclaimer: screening/education only—talk to a pediatric clinician for medical advice.
For adults 20+, use our Adult BMI Calculator. Browse more tools in our Health Calculators hub.
Child’s Details
Calculation Steps
- Enter details to see the steps.
Results
Table of Contents
Body mass index-for-age percentiles: Boys, 2 to 19 years
Chart loads when it scrolls into view (performance-optimized).
Calculation Breakdown
| Item | Value |
|---|---|
| Enter details to see the breakdown. | |
CDC BMI-for-Age Categories
| Category | Rule | Meaning |
|---|---|---|
| Underweight | < 5th percentile | Below the healthy weight range for age and sex |
| Healthy weight | 5th to < 85th percentile | Healthy weight range for age and sex |
| Overweight | 85th to < 95th percentile | Above the healthy weight range for age and sex |
| Obesity | ≥ 95th percentile | Significantly above the healthy range for age and sex |
| Severe Obesity | ≥ 120% of the 95th percentile OR BMI ≥ 35 kg/m² | Highest-risk screening category (subset of obesity). Medical guidance is strongly recommended. |
Child BMI Calculator FAQs
General guidance about child BMI. Consult a healthcare professional for personalized advice.
What age range does this calculator cover?
This calculator is for children and teens aged 2 to 19 years. For infants/toddlers under 2, different growth standards are used. For adults 20 and older, use an adult BMI calculator
Why does child BMI use percentiles instead of fixed categories?
Children’s body composition changes as they grow. A BMI value that’s typical at one age may be unusual at another. BMI-for-age percentiles compare a child’s BMI with others of the same age and sex in a reference population.
What reference data does this calculator use?
It uses the CDC BMI-for-age reference from the 2000 revised growth charts, using CDC LMS parameter data to convert BMI into a percentile.
Is this calculator accurate outside the United States (CDC vs WHO)?
This tool uses the CDC reference, commonly used for screening and education. Some countries or health systems use WHO references (or national growth charts). For country-specific interpretation, follow local clinical guidance.
What is a “normal” BMI for a child?
For ages 2–19, “normal” is usually discussed using percentiles, not a single BMI number. A common CDC screening definition of healthy weight is 5th to <85th percentile for age and sex.
How do you calculate BMI for kids?
First calculate BMI: weight (kg) ÷ height² (m²). Then interpret that BMI using a BMI-for-age percentile based on the child’s age (in months) and sex. This calculator performs both steps.
What does BMI percentile mean?
A percentile shows how a child’s BMI compares with a reference group of the same age and sex. For example, the 60th percentile means the BMI is higher than about 60% of peers in the reference data.
What BMI percentile is considered overweight or obese for kids?
Common CDC screening categories are:
Underweight: <5th percentile
Healthy weight: 5th to <85th percentile
Overweight: 85th to <95th percentile
Obesity: ≥95th percentile
These are screening categories, not a diagnosis.
What is “% of the 95th percentile”?
It estimates how far a child’s BMI is above the 95th percentile for their age and sex. It’s often used to describe severity within the obesity range (screening context only).
My child’s BMI percentile seems high. Should I be worried?
A single BMI reading is a screening tool, not a diagnosis. Growth spurts, puberty timing, muscle mass, and genetics can affect BMI. If you’re concerned—especially if the percentile is persistently high or rising over time—discuss it with a pediatric clinician.
Can BMI be misleading for athletic or muscular kids?
Sometimes. BMI doesn’t directly measure body fat and may not reflect body composition. A clinician can consider BMI alongside growth patterns and other health information.
Can you tell if a child is overweight from weight alone?
No. Weight alone can’t answer that. You need height, sex, and exact age to estimate BMI-for-age percentile. Use the calculator for a screening estimate, and consult a clinician for personalized interpretation.
Why does the calculator ask for age in months?
For children and teens, BMI percentiles depend on exact age. Small differences (for example, 13 years 0 months vs. 13 years 11 months) can change the percentile. Using age in months improves accuracy.
Is this CDC child and teen BMI calculator accurate?
It’s accurate for calculating BMI and estimating the CDC BMI-for-age percentile when measurements and age are entered correctly. However, BMI percentiles are a screening tool, not a diagnosis—clinicians interpret results alongside growth patterns, puberty timing, and overall health.
How to Use This Child BMI Calculator
- Select sex (used for the CDC BMI-for-age reference curves).
- Enter age in years and months (months improve accuracy).
- Choose metric (kg/cm) or imperial (lb/ft/in), then enter weight and height.
- Review BMI, percentile, category, % of 95th, and the chart.
Tip: measure height without shoes, standing straight, and re-check weight on a stable scale.
The Problem This Calculator Solves
For kids and teens, a BMI number by itself is not enough. The same BMI can be normal at one age and high at another. This calculator automates the two-step process:
- Compute BMI from height and weight.
- Interpret BMI using CDC BMI-for-age percentiles based on age in months and sex.
It also estimates a healthy weight range at the same height (5th–<85th percentile).
Worked Examples (Beginner + Real‑World)
Example 1 (Beginner): BMI math
- Age: 10y 6m (enter years + months)
- Height: 138 cm (1.38 m)
- Weight: 32 kg
- BMI: 32 ÷ 1.38² = 32 ÷ 1.9044 ≈ 16.8
- Next step: the calculator uses age + sex to convert BMI into a percentile.
Example 2 (Real‑world): same BMI, different meaning
Two children can share the same BMI but land in different percentiles because their reference curves differ by age/sex. That’s why pediatric BMI uses percentiles rather than adult cutoffs.
- Child A: 8y boy, BMI 18 → percentile might be different than…
- Child B: 14y boy, BMI 18
- Takeaway: use percentiles to interpret, and track trends over time.
Prefilled CDC child & teen BMI calculator examples
These are real-world sample entries. Click an example to open the calculator prefilled (CDC BMI-for-age percentile method).
- cdc child teen bmi calculator boy 13 years 11 months 166.4 cm 47 kg — open prefilled example
- cdc bmi-for-age percentile calculator boy 13 years 11 months 166.4 cm 47 kg — open prefilled example
- cdc bmi percentile calculator 15 year old boy 171 cm 63 kg — open prefilled example
- cdc bmi percentile calculator child boy 13 years 11 months 166.4 cm 47 kg — open prefilled example
How to Calculate BMI for Kids (Formula + Method)
Step 1 — Calculate BMI
- BMI = weight (kg) ÷ height² (m²)
- If you use pounds and feet/inches, this calculator converts to metric first.
Step 2 — Convert BMI to a BMI‑for‑age percentile (CDC)
- Use the child’s age in months and sex to select CDC LMS parameters.
- Convert BMI to a z‑score using the LMS method, then convert z‑score to percentile.
What BMI Percentile Means (in plain English)
A percentile compares your child’s BMI to a CDC reference population of the same age and sex. For example, the 60th percentile means the BMI is higher than about 60% of same‑age, same‑sex peers in the reference data.
Percentiles are used for screening—clinicians also consider growth patterns, puberty timing, medical history, and body composition.
What Is a “Normal” BMI for a Child?
For ages 2–19, “normal” is typically discussed using percentiles rather than a single BMI number.
- Healthy weight: 5th to <85th percentile
- Underweight: <5th percentile
- Overweight: 85th to <95th percentile
- Obesity: ≥95th percentile
Puberty Timing Can Shift BMI Percentiles (Common Confusion)
During puberty, height and weight may change quickly and not always at the same time. This can temporarily shift BMI and percentile even when overall health is fine. If you notice a big percentile change, consider:
- Has height changed recently (or is a growth spurt starting)?
- Was measurement taken consistently (same scale, similar clothing)?
- Is the trend persistent over multiple measurements?
If the percentile remains high or rises over time, a pediatric clinician can interpret it in context.
Troubleshooting
- Results show “—”: check that age is 2–19 and months are 0–11.
- Percentile looks surprising: re-check height—small errors matter a lot.
- Imperial height errors: inches must be 0–11 (not 12).
- “Unusual values” warning: your entry may be outside typical ranges; re-check measurements.
CDC vs WHO BMI-for-Age: What’s the Difference?
This calculator uses CDC BMI-for-age (2–19) reference data. In some countries or systems, WHO references (or national growth charts) may be preferred.
- CDC: commonly used in the United States; provides LMS parameter files.
- WHO: provides growth references (including ages 5–19) plus separate standards for younger ages.
- Practical tip: if your clinic uses a specific chart, interpret results using that same reference.
Limitations of BMI in Children (Important)
- BMI doesn’t directly measure body fat. Athletic or muscular kids may be misclassified.
- Percentiles are reference-based. They don’t include medical history, puberty stage, or body composition.
- Use trends. One measurement can be misleading; patterns over time matter more.
When BMI can fail (examples)
- High muscle mass (some sports) → BMI may overestimate fatness.
- Fluid retention or some medical conditions → weight may not reflect fat mass.
- Rapid growth spurts → temporary percentile shifts.
Accuracy & Editorial Policy
- Data basis: CDC BMI-for-age (2000 revised growth charts) LMS parameters.
- Purpose: educational + screening only; not a diagnosis.
- Updates: logic and references reviewed periodically. Last updated: .
- Policies: see Editorial policy and Disclaimer.
Methodology (How This Calculator Works)
Method used: CDC child and teen BMI calculator approach (BMI-for-age percentile using CDC LMS parameters).
1) BMI calculation
- BMI = weight (kg) ÷ height² (m²)
- Imperial entries are converted to metric before calculation.
2) CDC BMI-for-age percentile
- Uses CDC 2000 growth chart LMS parameters for the selected sex and age (in months).
- Computes a z-score using the LMS method, then converts z-score to percentile using a normal distribution approximation.
3) Category interpretation
- Underweight: <5th percentile
- Healthy weight: 5th to <85th percentile
- Overweight: 85th to <95th percentile
- Obesity: ≥95th percentile
- Severe obesity (screening flag): ≥120% of the 95th percentile or BMI ≥35 kg/m²
Sources & Further Reading
This calculator uses CDC BMI-for-age growth chart reference data.