Baby Growth Percentile Calculator

See how your child's weight, length and head size compare with the WHO growth charts, from birth to 5 years.

This tool gives general estimates only and is not medical advice. Always follow the guidance of your healthcare provider.

How the percentile is calculated

This calculator uses the World Health Organization (WHO) Child Growth Standards. These are the charts recommended in the United States for children from birth to 2 years, and they cover children up to age 5. For your child's sex and exact age in days, the calculator looks up the WHO values and works out where the measurement falls, using the same method (called LMS) that growth chart software uses.

A percentile shows how a measurement compares with other children of the same age and sex. If your daughter's weight is on the 25th percentile, she weighs the same as or more than 25 in 100 girls her age, and less than the other 75. You only need to enter the measurements you have.

How to read the result

There is no "best" percentile. A healthy child can be on the 10th percentile or the 90th, and one is no better than the other. What doctors look for is steady growth. A child who follows roughly the same curve from one check-up to the next is usually growing well, wherever that curve sits.

The result also shows the range that most children fall within, from the 2nd to the 98th percentile. A measurement outside that range, or one that has moved a long way up or down the chart since the last visit, is a reason to talk to your pediatrician. It is not a diagnosis. These cut-offs are a screening guide, and your child's doctor will also consider their history and how they are doing overall.

Getting an accurate measurement

Weight: weigh your baby without clothes, or in a clean, dry diaper, on a baby scale. Ordinary bathroom scales are not precise enough for young babies.
Length: children under 2 are measured lying down, and children aged 2 and over are measured standing. Lying length is about 0.7 cm (¼ inch) more than standing height, so the chart changes at age 2.
Head circumference: wrap a flexible tape measure around the widest part of the head, just above the eyebrows and ears.

Small errors matter more for babies, so the measurements taken at your child's clinic are the ones to rely on.

Which charts does my doctor use?

In the United States, the CDC recommends the WHO charts from birth to 2 years and the CDC's own charts from age 2. This calculator uses the WHO charts for the whole range, so for children over 2 your doctor's percentile may be a little different.

The WHO charts describe how healthy children grow in good conditions. They are based on children in six countries, including the United States, most of whom were breastfed, and they are used for breastfed and formula-fed babies alike.

Babies born early

The WHO charts are based on babies born at term. If your baby was born before 37 weeks, ask your pediatrician which chart and which age to use. Doctors often use corrected age for the first two years.

Frequently asked questions

What is a normal percentile for a baby?

Any percentile between about the 2nd and the 98th is within the range that most healthy children fall in. A higher number is not better. Steady growth along a similar curve matters more than the number itself.

My baby has moved down the chart. Should I worry?

Small moves up and down are common, especially when measurements are taken on different scales. A large or continuing change is worth discussing with your pediatrician, who can check the trend with accurate measurements.

Do breastfed and formula-fed babies use the same chart?

Yes. The WHO charts are recommended for both. They are based on healthy children who were mostly breastfed, which is treated as the normal pattern of growth.

Why is my doctor's percentile different from this one?

Clinics may use different charts (for example the CDC charts from age 2), measure more precisely, or use your child's exact age on the day of the visit. Small differences in a measurement or in age can shift the percentile by several points.

Which matters most: weight, length or head size?

They are read together. Doctors look at whether weight and length are in proportion, and whether each measurement follows its own curve over time.