Child BMI Calculator
For Parents, Private, and Quick
Enter your child's age, height, and weight, and see how their BMI compares with the WHO growth charts.
Your entries stay in your browser. They leave it only if you choose to send your result on WhatsApp. Only your choice of units is remembered, on this device.
The result will appear here
Enter your child's age, height, and weight, for ages 5 to 19.
This tool starts at 5 years and 1 month
Younger children are measured on different growth charts, which this tool doesn't include. Your paediatrician can plot your child's growth, and a nutritionist can help with meals.
Nutrition support for childrenThis tool ends at 19 years
From this age on, the adult BMI calculator is the one to use.
Go to the adult BMI calculatorBMI-for-age
- BMI
- Z-score
How this was calculated
A child's BMI is compared with children of the same age and sex, using the WHO 2007 growth reference for 5 to 19 years, month by month. The LMS method gives a z-score, which shows how far the BMI is from the WHO median, and a percentile. WHO names the categories by z-score: thinness below −2, overweight above +1, and obesity above +2.
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One number can't describe a growing child. Please don't put your child on a diet because of this result. Talk to your paediatrician or a nutritionist first. This is an estimate for general information only, not medical advice.
What This Tool Shows
BMI compares weight with height. For adults it is read against fixed numbers, but children are still growing, and a healthy BMI changes with age and differs between boys and girls. So a child’s BMI is read against a growth chart.
This tool looks up your child’s age and sex, month by month, in the World Health Organization’s 2007 growth reference for 5 to 19 years. It then shows a percentile, a z-score, and which range your child falls in.
How to Read the Result
A z-score shows how far a BMI sits from the WHO median, which is the middle of the reference group. Zero is exactly in the middle. WHO names the ranges by z-score: thinness below −2, normal from −2 to +1, overweight above +1, and obesity above +2.
The percentile says the same thing another way. It is a position in a group, not a mark out of a hundred. A child at the 40th percentile hasn’t done worse than one at the 60th.
What One Number Leaves Out
BMI doesn’t measure body fat directly, and it can’t see muscle, build, or family traits. Children also often gain weight just before a growth spurt, and puberty arrives at different ages. That is why a single result matters less than how your child’s growth moves over time.
These charts are also international. An Indian paediatrician may use the IAP 2015 charts, which can give a somewhat different reading for the same child, so please don’t worry if theirs differs from this.
If You Are Concerned
Your paediatrician can measure your child properly and plot their growth over the years. That is the best next step if the result surprises you, or if your child’s appetite, energy, or weight has changed quickly.
Please try to keep talk about weight away from your child. Comments, even kind ones, can stay with children for a long time. It usually helps more to make healthy changes for the whole family: meals together, more outdoor play, and fewer sweet drinks.
If you would like help with meals for a fussy eater or for the whole family, a consultation can help you find what works at home.
Questions About Your Child's BMI
Clear Answers, No Jargon
Why can't I use the adult BMI calculator for my child?
Children's bodies change as they grow, so the same BMI can mean different things at 8 and at 16. A child's BMI is compared with children of the same age and sex, rather than with fixed cut-offs.
What does the percentile mean?
It shows where your child's BMI falls among the WHO reference group. At the 60th percentile, about 60 in 100 children of that age and sex in the reference have a lower BMI. It isn't a score, and a higher number isn't better.
Should I put my child on a diet?
Please don't, without speaking to a doctor first. Children need enough food to grow, and strict diets can do harm. Family meals, active play, and good sleep usually help more.
Why does this start at 5 years and 1 month?
The WHO tables used here run from 61 to 228 months. Younger children are measured on a different set of charts, which this tool doesn't include, so it shows a message instead.
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