Baby Percentile Calculator
Find baby weight, height, and head circumference percentiles from WHO growth standards for infants up to 24 months.
What Are Baby Growth Percentiles?
Baby growth percentiles compare your infant's weight, length, and head circumference to WHO Child Growth Standards for the same sex and age. A 50th percentile means half of reference infants are smaller and half are larger. Related tools: Baby Formula Calculator and Adjusted Age Calculator.
How Percentiles Are Calculated
This calculator uses WHO monthly median and standard deviation (SD) reference values for ages 0–24 months, with linear interpolation between months. For each measurement, the z-score is $(x - M) / SD$, and the percentile comes from the normal cumulative distribution.
Reading the Results
Consistent tracking along a percentile canal is usually reassuring. A sudden jump across multiple canals, or large differences between weight, height, and head circumference percentiles, may warrant discussion with your pediatrician. Percentiles describe population reference ranges—they are not grades.
Frequently Asked Questions
Which growth standard does this calculator use?
It uses WHO Child Growth Standards, the reference recommended by the CDC for infants and children under 24 months in the United States.
Do I need to enter all three measurements?
No. Weight, height, and head circumference are optional. Enter whichever measurements you have; the calculator shows percentiles only for values provided.
What is a normal baby percentile?
Any percentile between about the 3rd and 97th can be healthy if growth is consistent over time. The 50th percentile is the population median, not a target.
Can I use this for premature babies?
For preterm infants, use corrected age rather than chronological age. See our Adjusted Age Calculator to determine the appropriate age for growth comparison.
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