Calculate weight, standing-height or BMI percentiles using CDC 2000 references. For children under two, Cocoon keeps recorded growth without calculating percentiles. Ask your clinician to interpret any growth concerns.
Source: CDC 2000 Growth Charts, available free on the CDC website. Use does not imply endorsement by CDC, HHS or the United States Government.
How it works
Choose your child's sex and the measurement: weight, standing height or BMI.
Enter an age from 24 to 240 months, or 2 to 20 years.
Enter the measurement in the selected unit. Height means standing height from age two.
Bring your child's measurements and trend to your clinician for interpretation.
Check the input before interpreting the result
Use the child's age on the measurement date, not their age today when entering an older measurement. Keep the original value and unit together. For this calculator, height means standing height and BMI means an already calculated value in kg/m²; it does not calculate BMI from a weight alone.
Fictional input check: an appointment record says “4 years; weight 16 kg”. You can enter age 4 in years or 48 in months and choose weight in kg. Entering 4 in months would describe a different age and is outside this calculator's range. These values illustrate data entry, not a recommended weight.
For an infant, keep the dated measurements and ask the care team to use the appropriate chart. The growth topic guide and percentile definition explain the terms. A percentile is a comparison with a reference, not a health score or a feeding target.
Take a trend, not just a screenshot
Keep the original measurements, dates and any uncertainty with the result. The appointment checklist helps organise your question. If a number seems unexpected, check the inputs and discuss your concern with a clinician rather than changing care from a calculator result.
Reference pages checked 13 October 2026. The calculation uses the existing CDC reference implementation; this explanation does not constitute clinical validation.
Cocoon records infant measurements without calculating infant percentiles. From age two, it also supports CDC reference percentiles. Keep your questions alongside the record for your care team.
CDC 2000 weight-for-age, stature-for-age and BMI-for-age references for ages 2–20. These describe a reference population and do not diagnose an individual child.
Can I track growth under age two?
Yes. Cocoon records infant weight, length and head circumference and plots the measurements. This release does not calculate infant percentiles. Your clinician can assess growth using an appropriate infant chart.
Does this calculate head-circumference percentiles?
No. Cocoon keeps head-circumference measurements as recorded history, without reference percentiles.
Should I worry if a percentile changes?
A single percentile cannot determine health. Bring the trend and any concerns to your doctor or child-health nurse for interpretation.
These tools organise records and reference information. They do not assess health or replace care. For concerns about your baby, contact your clinician.