Baby Percentile Calculator

Created by Aleksandra Zając, MD
Reviewed by Dominik Czernia, PhD, Jack Bowater and Łucja Zaborowska, MD, PhD candidate
Based on research by
WHO, Nutrition and Food Safety team WHO child growth standards: growth velocity based on weight, length and head circumference: methods and development; WHO; November 2009
Last updated: Jan 18, 2024


If you ever want to monitor how your child is developing, our baby percentile calculator has got you covered. With our tool, you don't have to draw your infant boy growth chart (or your infant girl growth chart!) by hand anymore — it will tell you right away the percentile your child is in. Besides, we've covered topics such as exactly what a percentile is, what does percentile mean for babies and parents, and why doctors use pediatric infant growth charts with such willingness. Read on to find out more about baby growth percentile graphs!

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a physician.

If you're interested in more baby percentile parameters, check also:

Why do we use pediatric infant growth charts?

Infant growth charts are a must-have tool in every pediatrician's office. They're a very simple, easy-to-use way of assessing various parameters of your child quickly. They are also a part of standard medical checkups.

The most important thing about baby growth percentile charts is that they let the doctor track the child's development. By plotting the data onto the graphs, they can observe if the baby is growing proportionately and quickly note any sudden changes. Here's an example infant boy growth chart:

Height/length chart for boys 0-2 years old according to WHO Child Growth Standards
Source - WHO Child Growth Standards

But at home, you no longer have to print the chart and laboriously plot your data onto it — you can use our calculator, and the result will be ready for you in a second!

What is a percentile? What does percentile mean for babies?

Percentile is actually a mathematical term. It tells us how many items/results are below and above the item/result that we are interested in for a specific group. Babies' growth charts tell us the percentage (%) of how many babies from the same group (age group, sex group) have measurements smaller than our baby.

Let's say we had a group of five people standing next to each other in height order. Their heights are 158 cm, 166 cm, 171 cm, 173 cm, and 180 cm. Their sex, age, or hair color don't matter in this example.

Five persons who stand next to each other in height order

The person who is 171 cm tall is in the 40th percentile, meaning 40% of people in this group are shorter than they are. The person who is 173 cm tall is in the 60th percentile, even though they are only 2 cm taller than the previous person.

What does percentile mean for babies, then? If your newborn is in the 50th percentile, that means 50% of all other babies are smaller than your baby. It is important to use the right charts — according to the baby's sex (there are individual infant girl growth charts and infant boy growth charts) and the country you are in. The USA's Center for Disease Control and Prevention recommends using the WHO's growth charts, which is what we have used in our calculator as well.

When and how to use baby percentile calculator

As the baby percentile calculator is only correct for certain groups, make sure the chart you're using is correct for your baby's age and sex. If your child is older than two years old, you might benefit from using the BMI percentile calculator, which is more appropriate for their age.

You should take a look at the graphs regularly to monitor your baby's development. Your pediatrician will also keep a copy, so don't be worried that you might miss something.

How to use the baby percentile calculator

Using the infant percentile calculator is straightforward. All you need to do is to:

  1. Fill in the necessities — your baby's sex.

  2. Provide their age. You can switch between years, months, and years or months separately. Remember that this infant growth calculator is intended for children up to the age of 24 months.

  3. Put in children's weight, height, and head circumference (head circumference reflects brain development). If you're not interested in some measurement, don't worry; you can leave them blank.

  4. Choose if you want to see a weight, height, or head circumference graph.

  5. Your result is ready immediately. Since you already know what does percentile mean, you can interpret it on your own, but we've provided you with some short comments as well.

Examples: infant boy growth chart & infant girl growth chart

Example 1

Let's imagine you are a pediatrician, and you're looking after a sweet baby boy — Tommy. Tommy is an active 14-month-old boy. He is already 80 cm tall, weighs 10.6 kg, and has a head circumference of 47.5 cm (you can find out more about measuring head circumference in the specific head circumference calculator).

Using our baby percentile calculator, we can quickly determine that Tommy is:

  • in the 50th percentiles for his weight;
  • in the 50th percentiles for his height; and
  • in the 50th percentiles for his head circumference.

Since Tommy has always been in those percentile canals, and he isn't presenting any abnormal symptoms, we know that he is developing perfectly. You can stay calm about his health!

Example 2

Your next patient is Samantha, who just turned three months old. This is one of her first doctor's appointments, but she's not annoyed at all. You take her measurements: her length is 65cm, weight — 7.3 kg, and head circumference — 42.5cm. This baby percentile calculator tells you that:

  • Samantha is between the 85th and 97th percentiles for her weight;
  • between the 85th and 97th percentiles for her height; and
  • between the 85th and 97th percentiles for her head circumference.

Looking back at her measurements, you notice that she has always been in these higher percentile canals, and you can't miss that both her parents are tall and slim. When they tell you about her behavior, milestones, and overall development, everything seems normal. Despite being so large for her age, Samantha is healthy and will probably turn out to be one of the tallest people around :-)

Baby growth percentile of my newborn is (...). What do I do now?

The percentiles in pediatrics are not rigid indicators; it's not like 'small John is in the third percentile, so he must be very sick'. Like many test results in medicine — you need to take the whole baby into consideration. Also, it's not an exam, not about better and worse results — being in the 90th percentile is not 'better' than being in the 15th percentile.

Overall, if a child follows the same percentile canal during their growth, and the results from other measurement charts are consistent, it usually means everything is fine. Consistent means that there are no big differences between height, weight, and head circumference graphs. Being mostly in the 50th percentile and in 85th for, e.g., height is rather normal. Still, a difference above two canals is a red flag, and you should refer to a pediatrician immediately.

That's also why a single percentile value is not worth much. It's the trend, the direction the child is going, not a single point of it.

Even if a child is small and stays below the 15th percentile all the time, they are probably perfectly healthy. They're just smaller, just like some adult people are shorter than others. This happens mostly if their parents are not tall and they were in similar percentile too when they were young. The same happens for the high baby growth percentile.

On the other hand, if a child was always in the 85th percentile and now suddenly drops down to the 15th percentile, it is a serious sign. It might be due to 'simple reasons', like not eating enough and malnutrition, but it could also be due to a serious medical condition.

To sum up, let's highlight the red flags that can be spotted in the pediatric infant growth chart:

  1. 🚩 A baby suddenly changes percentile pattern (up or down), especially when it is visible only in one measurement;
  2. 🚩 A baby doesn't grow taller at the same rate they're gaining weight — when the canals for weight and height are not consistent

So, a general rule is — if your child follows a certain percentile canal, if their development is fine in your assessment, if they're growing proportionately and don't present any disturbing signs, you probably don't have anything to worry about.

And last but not least, we need to repeat the disclaimer here — if anything health-related bothers you or your kid, talk to your doctor.

FAQ

What does the 95th percentile mean for baby weight?

If a baby is in the 95th percentile for weight, the baby's weight is greater than or equal to 95% of babies of the same age and sex. You can use the Omni baby percentile calculator to determine the percentile your baby is in.

What is a good percentile for a baby?

A good percentile for a baby depends on various factors, and the percentiles in pediatrics are not rigid indicators. If a baby consistently tracks along the same percentile curve for their growth, and the measurements from other growth charts remain consistent, it typically indicates that everything is proceeding as expected.

What is my baby's height percentile if he is 80 cm tall?

If your baby is 14 months old and 80 cm tall (31.5 inches), his height falls within the 85th to 97th percentile. You can use the Omni baby percentile calculator to determine where your baby's weight and head circumference fall in the percentiles.

How do I measure a baby's head circumference?

To measure a baby's head circumference, you can follow these steps:

  1. Find a flexible and non-stretchable measuring tape.

  2. Gently wrap the tape around your baby's head, ensuring it passes just above the eyebrows, over the ears, and around the occipital prominence at the back of the head, near the base of the skull.

  3. Record the head circumference, rounding it to the nearest 0.1 cm for precise measurement.

Aleksandra Zając, MD
My baby is a....
girl
Age
mos
Weight
lb
Height
in
Head circumference
in
Chart
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weight chart
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Birthweight percentileChild BMI percentileChild height percentile… 4 more
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