BMI Percentile Calculator

BMI Percentile Calculator for Pediatrics. The result reports the raw BMI, a reference z-score and a percentile. At or above the 97th percentile, the output directs the reader to the CDC 2022 extended BMI reference. A conventional LMS upper tail should not be treated as a precise measure of extreme obesity severity.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

BMI is weight in kilograms divided by height in meters squared. The resulting value is compared with the CDC 2000 BMI LMS parameters for sex and age, with linear interpolation between published knots. The supported range is 24-240 months; this is not an adult BMI-band calculation or a WHO standard.

When to use this calculator

Use the page to learn how the same raw BMI can have different reference positions at different childhood ages. Record a reliable standing height and weight. The endpoint at 240 months is a reference-chart endpoint, not a recommendation to continue pediatric clinical categories indefinitely.

Inputs used

  • Age (months)
  • Sex used by the reference
  • Measured weight (kg)
  • Standing height (cm)

Clinical interpretation

The result reports the raw BMI, a reference z-score and a percentile. At or above the 97th percentile, the output directs the reader to the CDC 2022 extended BMI reference. A conventional LMS upper tail should not be treated as a precise measure of extreme obesity severity.

Worked example

For a male reference at 24 months, weight 16.57502768 kg and height 100 cm give BMI 16.57502768 kg/m2, exactly the published median and therefore the 50th percentile. Separately, weight 42 kg and height 140 cm give raw BMI 21.4286; its percentile must be obtained from the entered age and sex.

Limitations and safety notes

The page does not implement the 2022 extended-BMI model, a diagnosis or a treatment plan. Measurement error and body composition affect interpretation. The numeric source is CDC/NCHS, available free from CDC; the public-domain methods report and agency reuse policy are linked. CDC, HHS and the U.S. Government do not endorse this independent implementation.

Frequently asked questions

Are adult BMI cutoffs used?

No. The raw BMI is compared with an age- and sex-specific CDC reference.

Can ages above 19 years be entered?

The reference endpoint of 240 months is supported, with its scope stated explicitly; values beyond it are rejected.

Why is an upper-tail warning shown?

The conventional CDC 2000 LMS reference is not the extended 2022 model used for more informative assessment of very high BMI.

References

  • CDC/NCHS reference identity, age ranges, LMS equations, sex encoding and allowance for interpolation. https://www.cdc.gov/growthcharts/cdc-data-files.htm
  • WHO reference recommendation below age two and interpretation around chart transitions. https://www.cdc.gov/growth-chart-training/hcp/using-growth-charts/who-using.html
  • Agency reuse requirements: attribution, non-endorsement, unchanged substantive data and free availability; exceptions are acknowledged. https://www.cdc.gov/other/agencymaterials.html
  • NCHS 2000 growth-chart methods report explicitly identifies its material as public domain. https://stacks.cdc.gov/view/cdc/6451/cdc_6451_DS1.pdf
  • Downloaded2026-09-09:438 CDC BMI rows, both sexes, original LMS and P3/P50/P97 columns; duplicate header skipped; 240.5-month rows retained only for interpolation. https://www.cdc.gov/growthcharts/data/zscore/bmiagerev.csv

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 9, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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