Child BMI Calculator

Calculate a child’s BMI from weight and height; this page does not assign a percentile or category.

Calculate BMI from a child’s measured weight and height. BMI is weight divided by height squared; this calculator does not estimate a child’s percentile or assign a weight category.

Children’s BMI is interpreted using age- and sex-specific growth references. Use an official pediatric calculator and discuss concerns about growth with a clinician.

Choose metric or US customary units.
Enter a positive weight and standing height.
Check the BMI arithmetic result and its units.
For growth interpretation, use an official age- and sex-specific calculator linked below.

BMI formula and scope

Metric: BMI = weight in kilograms ÷ height in metres². US customary: BMI = 703 × weight in pounds ÷ height in inches².

This calculator reports the BMI arithmetic only. It does not apply adult cut-offs, calculate BMI-for-age percentiles, or diagnose a health condition.

How to read the BMI result

A number, not a pediatric category

The displayed value is a screening measurement derived from weight and height. For children and adolescents, clinicians interpret BMI with age- and sex-specific percentiles and growth history; a single BMI value is not a diagnosis. Use the CDC Child and Teen BMI Calculator or consult a clinician.

Health tips and best practices

Measure height without shoes and use a reliable scale.
Keep units consistent with the selected system.
Ask a pediatric clinician to interpret growth or a changing pattern.

Worked example: at 30 kg and 130 cm, height is 1.30 m; BMI = 30 ÷ (1.30 × 1.30) = 17.75 kg/m² (rounded to two decimals). This is an arithmetic example only and is not a percentile or category.

Common mistakes to avoid

Using adult BMI thresholds to classify a child.
Entering centimetres where metres are required in a manual calculation.
Interpreting one measurement without age, sex, growth pattern, and clinical context.

Non-diagnostic information only. This result cannot assess a child’s health or growth. Talk to a doctor or pediatric clinician about interpretation, concerns, or next steps. The official CDC calculator provides BMI-for-age interpretation for ages 2–19.