Weight Percentile Calculator

Created by Dominika Śmiałek, MD, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Based on research by
The WHO Multicentre Growth Reference Study WHO Child Growth Standards (2006)
Last updated: Dec 22, 2022

Are you curious about your baby's development? Then this weight percentile calculator is designed exactly for you! You'll learn in which percentile your child places, how that relates to their peers, and, most importantly - how baby weight percentiles can describe a child's health from birth. That's not all - in the article below we explain why we use percentiles, how to interpret the WHO growth chart, and we'll show you a quick example of how this infant growth chart calculator is used.

If you want to assess the height of your kid, use out height percentile calculator

So, if you've ever asked yourself "what percentile is my baby?", stay with us and read on.

The aim of the baby weight chart

When assessing a baby's weight, a percentile scale is used. As most children have a specific time where they grow rapidly, require more calories and reach many developmental milestones, it's not easy to know what your child should weight at any particular age.

Therefore, the WHO has developed a baby weight chart, which describes the typical trajectory of a kid's development. With this infant growth chart, you don't look solely at how much they weigh, their height, or their BMI, but where among their peers the child is. Also, the baby may gain weight before they begin to grow much taller, or vice versa. You may check their BMI with our BMI calculator for kids

How to interpret the baby percentile chart?

As mentioned above, raw kilograms are not used when assessing a child's development. However, you always refer to them when calculating the appropriate ibuprofen or paracetamol dose per kg of body weight.

Doctors consider the rate of growth as an important factor when looking at an infant growth chart:

  1. The child should follow the same percentile line on the baby growth chart as they gain weight.
  2. If the results cross two or more percentile lines (they raise/decrease by at least two ranges), e.g. from the 75th-85th percentile to the 15th-25th percentile, you should consult a doctor.
  3. Again, if their weight is below the 5th or above the 95th percentile, check if the baby has always been in those ranges. If your child has only entered these ranges recently, consult a doctor. Also, a visit at a dietitian may be useful - as well as controlling their daily calorie intake.
WHO weight for age chart - girls
Girls chart - weight for age, World Health Organization, Licence: CC BY-NC-SA 3.0 IGO
WHO weight for age chart - boys
Boys chart - weight for age, World Health Organization, Licence: CC BY-NC-SA 3.0 IGO

Our data derives from the WHO (World Health Organization), and the standards were developed using data collected in the WHO Multicentre Growth Reference Study. This tool can be only used if a child is less than five years old. After that age, BMI percentile calculator becomes more indicative of a child's development.

Baby weight percentile calculator - how to use it

Let's explain how to use this kids growth chart calculator:

  1. First, give us some details:

    • Age of your child - (either in weeks, months, or even years). The tool is based on a monthly baby weight chart (for kids older than 13 weeks) or by week (for those younger). Note, that the tool provides information only for children up to 5 years old.
    • Whether they're a boy or a girl.
  2. Fill in the weight of your child. You can easily use the in-built weight converter to switch between units.

  3. Get the results.

Now you'll know the answer to the crucial question, "what percentile is my baby?". The first number is the exact baby percentile, and the second is which percentiles they fit into, with an explanation. There's also a graphic explaining where this percentile is with respect to other children.

The weight of the baby also helps estimate the baby's milk intake requirement.

Weight percentile calculator in practice

It's time to show you how this baby weight percentile calculator works - with an example. Let's take Yvonne, a 31 year old mum of two. The younger one, Vincent, is now five months old. At birth, he received 9 out of 10 in the APGAR score, and his development has always seemed normal, with both weight and height falling perfectly between the 50 and 75th percentiles.

Two weeks ago, Vincent had a little cold, and Yvonne took him to the pediatrician, who checked his percentiles (with the use of our tool and the WHO growth chart).

The doctor calculated: age: 5 months, sex: male, weight: 6.38 kg. The result was clear, the 8th percentile, exactly between the 5th and 10th percentiles.

What does it mean? Something has changed, and the child needs some further diagnostics. The baby percentile chart result itself is quite correct, but as Vincent has dropped by more than 2 percentile lines - his BMI and head circumference percentiles need to be checked.

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.


What is the child weight percentile?

The child weight percentile is defined as the comparison of weights between the child and the rest of the children among the group of 100. Such that, if the weight percentile is 80, the child is likely to have more weight than 80 children in the group, and less weight than the other 20. The idea is to compare the weight and/or size of the baby compared to their peers.

What do I need to find the child weight percentile?

To find the child weight percentile, you would need:

  • The age of your child,
  • The weight of your child, and
  • WHO child growth chart.

How do I estimate the child weight percentile?

To estimate the child weight percentile:

  1. Mark the age of your child on the WHO growth chart and trace a horizontal line
  2. Similarly, mark the weight of your child on the X-axis of the growth chart and draw a vertical line, until it meets the horizontal line.
  3. The percentile curve on which the intersection occurs is the weight percentile of the child.

Should my child follow the same percentile line?

The child should follow the same percentile curve as they grow older. If they go up or down by 2 percentiles for any reason, you should consult a doctor.

Dominika Śmiałek, MD, PhD candidate
Is it a boy or a girl?
Girl ♀️
The exact result is:
Check out other percentile caculators:

✔️ Height
✔️ Head circumference
✔️ BMI

This tool is based on WHO's child growth standards.
Check out 7 similar percentile calculators 👶
Baby percentileBirthweight percentileChild BMI percentile… 4 more
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