Baby Weight Percentile Calculator
See where your baby falls on the WHO growth chart. Enter weight, height, and age to get instant percentile results based on the same WHO standards pediatricians use worldwide.
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Growth History
Save measurements to track trends over time (stored privately on your device).
Understanding Baby Weight Percentiles
A baby weight percentile tells you how your child's weight compares to other children of the same age and sex. If your baby is at the 60th percentile for weight, it means they weigh more than 60% of babies their age and less than 40%. Pediatricians around the world use percentile charts as a standard tool at every well-child visit to track growth over time.
Our calculator uses the WHO Child Growth Standards, published in 2006 and based on a landmark study of healthy, breastfed children from six countries (Brazil, Ghana, India, Norway, Oman, and the United States). These standards describe how children should grow under optimal conditions — making them the gold standard for assessing growth in children from birth to 24 months.
How the WHO Growth Chart Calculator Works
The WHO growth charts use a statistical method called the LMS technique (Lambda-Mu-Sigma). For each age and sex combination, three parameters describe the distribution of measurements: L (the Box-Cox power for skewness), M (the median), and S (the coefficient of variation). When you enter your baby's weight, age, and sex, the calculator converts the measurement into a z-score using these parameters, then translates that z-score into a percentile.
This calculator provides three key measurements: weight-for-age (how your baby's weight compares to others at the same age), height-for-age (how your baby's length compares to others at the same age), and weight-for-height (whether your baby's weight is proportional to their length). Together, these three percentiles give a more complete picture than any single number.
What Do the Percentile Numbers Mean?
Any percentile between the 3rd and 97th is considered within the normal range. There is no "ideal" percentile — a baby consistently tracking along the 20th percentile is just as healthy as one tracking along the 80th. What pediatricians watch for is crossing percentile lines: a sudden jump up or down across two or more major lines can signal a feeding issue, illness, or other concern worth investigating.
Percentiles below the 3rd or above the 97th may warrant further evaluation, but they are not automatic causes for alarm. Genetics, premature birth, and feeding method (breast vs. formula) all influence where a baby falls on the chart. The most important factor is consistent growth along your baby's own curve over time — which is why saving and comparing measurements at each doctor visit matters more than any single reading.
Frequently Asked Questions
What is a normal baby weight percentile?
There is no single "normal" percentile. Any percentile from the 3rd to the 97th is considered within the normal range. What matters most is that your baby follows a consistent growth curve over time. A baby in the 15th percentile is just as healthy as one in the 85th — it simply means they are smaller or larger compared to other babies of the same age and sex.
Is the 50th percentile average?
Yes, the 50th percentile represents the median — meaning half of babies weigh more and half weigh less at that age. However, being at the 50th percentile is not a "goal." Babies come in all healthy sizes. A baby consistently at the 20th or 80th percentile is growing perfectly normally.
When should I worry about my baby's weight?
Consult your pediatrician if: your baby falls below the 3rd or above the 97th percentile, their growth curve crosses two or more major percentile lines (up or down) in a short period, or they show signs of poor feeding, lethargy, or other concerning symptoms. A single measurement is rarely a cause for concern — patterns over time matter much more.
How do I read a baby growth chart?
Growth charts plot your baby's measurements against standard curves. The curves represent percentile lines (3rd, 15th, 50th, 85th, 97th). Find your baby's age on the horizontal axis, then trace up to their weight or length. Where it falls relative to the percentile curves shows how they compare to other babies. The most important thing is consistency — following the same approximate curve over time.
What are WHO Growth Standards?
The WHO Child Growth Standards (2006) describe how children should grow under optimal conditions. They are based on data from healthy, breastfed children from six countries (Brazil, Ghana, India, Norway, Oman, and USA). These standards are used by pediatricians in over 140 countries as the reference for assessing child growth from birth to 5 years.
What is the difference between weight-for-age and weight-for-height?
Weight-for-age compares your baby's weight to other babies of the same age and sex. Weight-for-height (also called weight-for-length) compares your baby's weight to other babies of the same height, regardless of age. Weight-for-height is especially useful for identifying if a baby is proportionally heavier or lighter for their body size.