Health Calculators
BMI for age percentile calculator.
For ages 2 to 19, BMI means little on its own: the same number reads differently at 8 and at 16. Enter sex, age, weight and height to get the CDC percentile and category. Runs in your browser; nothing is sent or stored.
Child or teen
BMI-for-age
Fill the form and press Get BMI percentile.
How the percentile is worked out
- BMI: weight in kilograms divided by height in metres squared.
- Reference values: CDC publishes three numbers for each sex and age, L (skew), M (median) and S (spread), for ages 2 to 20 in half-month steps. This page interpolates between neighbouring ages, as CDC advises for finer ages.
- z-score: z = ((BMI ÷ M)L − 1) ÷ (L × S). A z of 0 is the median.
- Percentile: the share of the reference population below that z on the normal curve.
Worked example. A boy aged 10 years who weighs 35 kg at 140 cm has a BMI of 17.9. For boys at that age the CDC 5th, 85th and 95th percentile BMIs are 14.2, 19.4 and 22.1, so his percentile is 70.6 (z = 0.54), which falls in the healthy weight category.
CDC weight categories for ages 2 to 19
| Category | BMI-for-age percentile |
|---|---|
| Underweight | Below the 5th |
| Healthy weight | 5th up to, not including, the 85th |
| Overweight | 85th up to, not including, the 95th |
| Obesity | 95th or higher |
| Severe obesity | 120% of the 95th percentile BMI or higher, or a BMI of 35 or higher |
The American Academy of Pediatrics splits severe obesity further: class 2 is 120% to under 140% of the 95th percentile (or BMI 35 to under 40), and class 3 is 140% or more (or BMI 40 or more), according to the CDC page above. This calculator flags severe obesity but does not split it into classes.
More worked examples
- A girl aged 15 years, 75 kg, 160 cm. BMI 29.3. Her 95th percentile BMI is 28.1, so she is at 104% of it, at the 96.2th percentile: obesity category, not severe obesity.
- The same BMI at two ages. A BMI of 20.0 is at the 94.9th percentile for a boy of 8 (overweight category) and at the 42.1th for a boy of 16 (healthy weight). That is why adult cut-offs like 25 and 30 do not apply to children.
What a percentile does and does not say
A percentile compares one child with the CDC reference population of the same age and sex. The 70th percentile means a BMI higher than about 70 out of 100 children in the reference group. It is not a grade. Children’s BMI shifts quickly through puberty, and muscular or tall-for-age children can have a high BMI without excess fat. BMI-for-age is a screening measure; a paediatrician looks at growth over time and the whole child, and may do further checks.
The CDC 2000 charts are based mostly on data from 1963 to 1980 and, in CDC’s words, do not extend beyond the 97th percentile. For children well above that level, CDC publishes extended BMI-for-age charts built on more recent data. This page shows when a result is beyond the 97th percentile so you can ask a clinician which chart they use. CDC’s BMI-for-age data file covers ages 2 to 20, so this calculator starts at 24 months.
Common mix-ups
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Often assumedA child is overweight at a BMI of 25 and has obesity at 30, the same as an adult.
What the source saysFor ages 2 to 19 the CDC uses percentiles for age and sex: overweight from the 85th up to under the 95th percentile, obesity at the 95th or higher, and severe obesity at 120% of the 95th percentile BMI or a BMI of 35 or more. [1]
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Often assumedThe standard CDC 2000 charts can show how far above the norm a very high BMI is.
What the source saysCDC says the 2000 BMI-for-age charts, built mostly on 1963 to 1980 data, do not extend beyond the 97th percentile, and publishes extended charts to monitor very high BMI values. [2]
Checked against these sources on .
FAQ
What is a healthy BMI percentile for a child?
The CDC calls the 5th percentile up to, but not including, the 85th the healthy weight range for ages 2 to 19. Underweight is below the 5th, overweight is 85th to under 95th, and obesity is the 95th and above.
Why do children use percentiles instead of the adult BMI scale?
Children’s BMI changes as they grow, and it differs between boys and girls. A fixed cut-off like 25 would mislabel many children, so CDC compares each child with others of the same age and sex.
Which growth chart does this use?
The CDC 2000 growth charts, using the BMI-for-age LMS parameters CDC publishes for ages 2 to 20. The data have not changed since the charts were first released on 30 May 2000.
My child is above the 97th percentile. Is the number still right?
The calculation extends the same curve, but CDC says the 2000 charts do not extend beyond the 97th percentile and publishes extended charts for very high BMI. Ask your child’s clinician which chart they use.
Can I use this for a child under 2?
No. The CDC BMI-for-age data file this page uses starts at age 2 (24 months), so younger children are outside its range.
Does a high percentile mean a child is overweight?
It is a screening result, not a diagnosis. BMI does not separate muscle from fat, and a single reading says nothing about growth over time. A paediatrician or family doctor can put it in context.
Sources
Official sources used on this page, retrieved October 2026 (2026-10-26). The L, M and S values come from the CDC data file bmiagerev.csv, downloaded on 2026-10-26.
- CDC: Growth chart training, data files (BMI-for-age, 2 to 20 years): the bmiagerev file, the L, M and S formulas, and the note that the data are unchanged since the 30 May 2000 release; page last reviewed 2024-09-02 (retrieved 2026-10-26)
- CDC: BMI categories for children and teens: the percentile cut-offs for underweight, healthy weight, overweight, obesity and severe obesity; page dated 2024-06-28 (retrieved 2026-10-26)
- CDC: Extended BMI-for-age growth charts: the 2000 charts rest mostly on 1963 to 1980 data and do not extend beyond the 97th percentile; page last reviewed 2024-09-02 (retrieved 2026-10-26)
Disclaimer
Educational estimate, not medical advice. BMI-for-age is a screening tool, not a diagnosis. Talk to your child’s doctor about growth and weight rather than acting on this number alone.