BMI Calculator for Children 2026 — Free Online

Calculate your Body Mass Index (BMI) instantly using our free online BMI Calculator. BMI is a widely used screening tool that estimates whether you are at a healthy weight relative to your height. Results show your BMI value with healthy weight range, category (underweight / normal / overweight / obese), and actionable health context. Enter your height and weight, and the calculator instantly shows your BMI score, weight category, and healthy weight range. No sign-up required — runs entirely in your browser.

Frequently Asked Questions

How is BMI calculated for children?

Children's BMI uses the same formula (weight ÷ height²) but is interpreted using age- and sex-specific percentile charts, not fixed ranges. A BMI in the 85th–94th percentile is 'overweight'; 95th percentile and above is 'obese'. The CDC and WHO provide separate charts for boys and girls aged 2–20 years.

What BMI percentile is healthy for a child?

A healthy BMI for children is between the 5th and 84th percentile for their age and sex. Below the 5th percentile is underweight; 85th–94th is overweight; 95th and above is obese. Percentiles naturally shift with age, so a child's BMI should be tracked over time, not judged at a single point.

When should I be concerned about my child's BMI?

Consult a paediatrician if your child's BMI percentile is below the 5th or above the 85th percentile, or if it has changed significantly in a short period. Rapid BMI gain in children can indicate early metabolic risk. BMI is a screening tool — a doctor will assess nutrition, activity, and growth trends together.

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