Baby percentile calculator
Enter your baby's age and measurements to see where they sit on the official WHO growth standards, for weight, length and head circumference. Nothing is stored.
How to read the result
A percentile is a ranking against other babies of the same age and sex, not a grade. The 30th percentile means 30 out of 100 babies weigh less. What matters clinically is the shape of the curve over months: steady tracking along any line is reassuring, while crossing two or more major lines downward is the pattern to raise with your doctor.
The z-score is the same information in standard deviations, where 0 is the median. A z-score between -2 and +2 covers about 95 percent of healthy babies.
Which chart this uses
Calculations run against the WHO Child Growth Standards, covering 0 to 5 years for both sexes. For a fuller explanation see baby growth percentiles explained. This tool is general information, not medical advice.
Frequently asked questions
How is the baby percentile calculated?
It uses the official WHO Child Growth Standards LMS tables for weight-for-age, length-for-age and head-circumference-for-age, the same reference most paediatricians use for children under 5.
What does the 50th percentile mean?
It means half of babies the same age and sex are smaller and half are larger. It is a ranking, not a target, and healthy babies sit at every percentile on the chart.
Should I use WHO or CDC charts?
WHO standards are recommended for children under 2 because they describe how healthy, largely breastfed babies grow. CDC charts are typically used from age 2 upward in the United States.
Is a low percentile a problem?
Not on its own. Doctors watch the trend across visits rather than a single number. Crossing two or more major percentile lines downward is the pattern worth asking about.