Parenting

Toddler BMI Calculator

Calculate BMI-for-age percentile for children ages 2-20 using CDC growth charts.

Quick Answer

For children 2-20, BMI is plotted on age-specific growth charts. Healthy weight falls between the 5th and 84th percentile. A 5-year-old boy who is 43" tall and weighs 42 lbs has a BMI of about 16.0, which is typically in the healthy range.

BMI

16.0

Percentile

57.5th

Category

Healthy Weight

CDC Percentile Ranges

UnderweightBelow 5th percentile
Healthy Weight5th to 84th percentile
Overweight85th to 94th percentile
Obese95th percentile and above
Medical Disclaimer:This calculator provides approximate BMI percentile using simplified CDC growth reference data. It is a screening tool, not a diagnosis. Always consult your child's pediatrician for proper growth assessment and health guidance.

About This Tool

The Toddler BMI Calculator computes Body Mass Index for children ages 2-20 and plots the result against CDC age- and sex-specific growth charts. Unlike adult BMI, children's BMI is expressed as a percentile because healthy ranges change as kids grow.

Why Percentiles Matter

A BMI percentile tells you how your child compares to other children of the same age and sex. The 50th percentile means your child's BMI is right at the median. What matters most is the trend over time — sudden changes in percentile rank are more concerning than any single measurement.

Limitations of BMI for Children

BMI doesn't measure body fat directly. Very athletic children with more muscle mass may have a higher BMI without being overweight. Similarly, a child with low muscle mass could have a "healthy" BMI but be carrying excess fat. Your pediatrician uses BMI alongside other assessments.

Frequently Asked Questions

Why is BMI calculated differently for children?
Unlike adults who use fixed BMI categories, children's BMI is compared to age- and sex-specific growth charts. A BMI of 18 might be healthy for a 10-year-old but underweight for a 16-year-old. The CDC uses percentile rankings rather than fixed cutoffs.
What BMI percentile is healthy for children?
The CDC defines healthy weight as the 5th to 84th percentile. Below the 5th is underweight, 85th to 94th is overweight, and 95th or above is obese. These categories apply to children ages 2-20.
Is BMI accurate for children?
BMI is a screening tool, not a diagnostic test. It doesn't distinguish between muscle and fat. Athletic, muscular children may have a high BMI but healthy body composition. Your pediatrician considers BMI alongside growth trends, activity level, and family history.
When should I be concerned about my child's BMI?
Talk to your pediatrician if your child's BMI percentile is below the 5th or above the 85th, or if there's been a sudden change in their growth trajectory. A single measurement is less important than the trend over time.
What age range does this calculator cover?
This calculator uses CDC BMI-for-age charts for children ages 2-20. For children under 2, pediatricians use weight-for-length charts instead of BMI. After age 20, standard adult BMI categories apply.

You might also like

Parenting

Baby Weight Percentile

WHO growth chart percentiles by age.

⏱ instantParenting

Baby Shoe Size Calculator

Find baby shoe size from foot length in US, EU, and UK sizes.

⏱ instantParenting

Child Height Predictor

Predict adult height from parents' heights.

⏱ instant