Children's BMI and Weight Calculator

This is calculator is in beta. Any problems please let us know.


Enter a valid DOB

Enter a valid weight

Weight Categories

This allows you to check your childs weight against the overall population. According to the CDC these categories were chosen by an 'expert committee'.

Percentile Category
Under 5th percentile. Underweight
5th to less than 85th percentile. Healthy Weight
85th to less than 95th percentile. Overweight
95th percentile and above. Obese


Understanding Percentiles

A percentile is a way of dividing a population into 100 equal groups. For example; if you are above the 95th percentile, you would be in the top 5%.

The US CDC provides a large amount of growth charts that break down childhood weight and height data into a series of percentiles (source).

How to Use

  • Please measure height accurately (stand the child against a wall, mark where the top of their head is, and use a tape measure).
  • Enter an accurate weight (use 1 decimal place: e.g. 34.6 kg).

What's Wrong with BMI?

As children are still growing, a simple measurement of weight for height (as is BMI) is not appropriate. Children's growth happens at all different ages and stages, so instead of straight BMI, for children it is often referred to as BMI-for-age.

These calculators do not measure body composition (this is usually done using skinfold thickness), and BMI is not a diagnostic tool. If you have any concerns please consult your local physician.

See also the CDC BMI Calculator.

Due to data available from the CDC, results can only be broken down into 3rd, 5th, 10th, 25th, 50th, 75th, 85th, 90th, 95th, and 97th percentile groupings.


  • Jago, R., Baranowski, T., Baranowski, J. C., Thompson, D., & Greaves, K. A. (2005). BMI from 3–6 y of age is predicted by TV viewing and physical activity, not diet. International journal of obesity, 29(6), 557-564. Link
  • Brown, K. A., Ogden, J., Vögele, C., & Gibson, E. L. (2008). The role of parental control practices in explaining children's diet and BMI. Appetite, 50(2), 252-259 Link
  • Flegal, K. M., Wei, R., & Ogden, C. (2002). Weight-for-stature compared with body mass index–for-age growth charts for the United States from the Centers for Disease Control and Prevention. The American journal of clinical nutrition, 75(4), 761-766. Link

Last Updated 30 Dec 2014