BMI Calculator for Kids

This tool works out a child's BMI from height and weight, then places it on a percentile scale for their exact age (2–19) and gender, in either metric or imperial units. Percentiles matter here because a "normal" BMI number for a toddler and a teenager are very different values — the percentile tells you where a child sits relative to other children of the same age and sex, rather than against a fixed adult scale.

Step-by-Step Instructions

  1. Pick metric (kg, cm) or imperial (lbs, ft/in) with the radio buttons.
  2. Enter age (2–19) and select gender.
  3. Enter height and weight in the units you chose.
  4. Click "Calculate BMI."

Worked Example

A 10-year-old girl who is 138 cm tall and weighs 32 kg has a BMI of 32 ÷ 1.38² = 32 ÷ 1.9044 ≈ 16.8. This calculator's reference data for 10-year-old girls puts the 25th percentile at a BMI of 15.2 and the 50th at 16.9, so a BMI of 16.8 lands close to the 49th percentile — squarely in the healthy weight range.

Reading the Output

Results show the BMI to one decimal place, an interpolated percentile (e.g. "49th percentile"), and a category: under the 5th percentile is Underweight, 5th to 84th is Healthy weight, 85th to 94th is Overweight, and 95th and above is Obese.

Limitations

The percentile table here is a simplified reference, not a full clinical growth-chart dataset, so treat results as a close estimate. This calculator does not replace a doctor's assessment — always talk to a healthcare provider for a full evaluation of a child's growth.

Common Use Cases