Child BMI calculator for ages 2–19: enter height and weight in metric or imperial units to see the BMI-for-age percentile and WHO category for your child.
Body fat in children shifts a great deal as they grow, and boys and girls develop differently, so a BMI of 22 does not mean the same thing for an 8-year-old as for an adult. Instead, a child’s BMI is ranked against children of the same sex and age as a percentile or z-score. Here we use the WHO Child Growth Standards for ages 2–5 and the WHO Growth Reference 2007 for ages 5–19.
Age
WHO category
BMI-for-age
5–19 years
Thinness
below −2 SD (about 2nd percentile)
5–19 years
Overweight
above +1 SD (about 85th percentile)
5–19 years
Obesity
above +2 SD (about 98th percentile)
2–5 years
Wasted
below −2 SD
2–5 years
Overweight
above +2 SD
2–5 years
Obese
above +3 SD
In the USA, doctors work with CDC charts, which call the 85th–94th percentile “overweight” and the 95th upwards “obesity”; the answers tend to be close. One BMI reading is only a screening check — your paediatrician will look at the growth trend. Please do not put a child on a weight-loss diet without medical guidance; the kids diet chart has balanced meal ideas.
Common questions
Which percentile range is considered healthy?
On WHO references, roughly the 3rd to the 85th percentile for the child’s age and sex (the 5th–85th on CDC charts).
Should a child with a high BMI cut back on food?
Not without advice — see your paediatrician first. Usually the focus is on family meals, fewer sugary drinks, less screen time and more play, so the child can grow into their weight.
At what age does the adult BMI scale apply?
From around 19–20 years. Until then, teenagers should be assessed with BMI-for-age percentiles.
Why do WHO and CDC results differ slightly?
They use different reference groups and cut-offs, but for most children both point to the same broad category.
Checked against the sources listed. This is general guidance only and not a substitute for medical advice — please speak to your doctor about your own situation.