Enter your baby's date of birth, the date of the measurement and their weight, length or head circumference. The baby percentile calculator compares the numbers with the WHO Child Growth Standards — the reference most pediatricians use for children up to 2 years — and shows where your baby sits on the curve.
General information from online sources, not written by a doctor and not a substitute for individual medical advice. Recommendations may differ by country; ask your care team about your baby.
Nothing you type is sent anywhere: the calculation runs in your browser.
What does a percentile mean?
A percentile compares your baby with a large group of healthy babies of the same age and sex. A weight on the 40th percentile means that 40 out of 100 babies weigh less and 60 weigh more. It is not a grade: a baby on the 10th percentile can be just as healthy as one on the 90th.
| Percentile | What it usually means |
|---|---|
| 3rd–97th | The typical range. Most babies fall here. |
| Below the 3rd or above the 97th | Worth discussing with your pediatrician, who will look at the whole picture. |
| Crossing two major lines | A curve that suddenly crosses two main percentile lines (for example from the 50th to below the 15th) matters more than any single number. |
The trend matters more than one measurement
Doctors look at how your baby grows over time. Healthy babies usually follow their own curve, roughly parallel to the printed lines. One measurement on a different scale, a full diaper or a wriggly baby can easily shift the result a little — so measure in the same way each time, ideally at the same clinic.
Premature baby? Use the corrected age calculator first and enter the date of birth shifted by the weeks your baby was born early, as your doctor advises. Want to know more? Read our guide to baby weight and growth percentiles.
This tool does not diagnose. Talk to your pediatrician if your baby's weight drops across percentile lines, if your baby is feeding poorly, has few wet diapers or seems unwell. Only a doctor can interpret growth in context.
Track growth automatically
In the baby tracker app Trackeron you log every weight and length and see them on WHO percentile charts over time — ready to show at your next check-up. Keep a full baby log alongside it to spot patterns in feeds and sleep.
See your baby's growth curve over time
Log weight and length in Trackeron and follow them on WHO percentile charts. Free to download for iPhone and Android.
Frequently asked questions
Which growth charts does this calculator use?
It uses the WHO Child Growth Standards (2006) for children from birth to 24 months, which are the international reference used by many health services.
Is a low percentile bad?
Not by itself. A baby who steadily follows the 5th or 10th percentile is often perfectly healthy. What matters is the trend over time and how your baby is feeding and developing — your pediatrician will look at the whole picture.
Why is my result different from the clinic?
Different scales, clothing, a full diaper and rounding all change the result slightly. Some countries also use national growth charts. Always follow your own doctor's charts.
Should I use corrected age for a premature baby?
Usually yes, until around 2 years of age. Ask your pediatrician how they prefer to plot your baby's measurements.
Is my data stored?
No. The calculation happens in your browser and nothing is sent or saved.