Baby Growth Percentiles Explained

If your pediatrician said your baby is "in the 50th percentile" — or the 10th, or the 90th — and you weren't sure whether that was good news, you're not alone. Here's what growth percentiles actually mean, in plain language.

What is a growth percentile?

A percentile compares your child to other children of the same age and sex. It answers one question: out of 100 children, how many weigh (or measure) less than yours?

If your 6-month-old daughter is in the 70th percentile for weight, that means she weighs more than 70 out of 100 girls her age, and less than the other 30. The percentiles used on this site come from the World Health Organization (WHO) Child Growth Standards, the international reference for children from birth to age 5.

What does the 50th percentile mean?

The 50th percentile is the median — the exact middle. A baby at the 50th percentile is bigger than half of their peers and smaller than the other half. It is the line most people picture as "average."

Importantly, the 50th percentile is not a target or a goal. There is nothing healthier about being at the 50th than at the 25th or the 75th. Perfectly healthy babies are spread right across the chart.

Percentile ranges at a glance

Percentile range	What it generally suggests
Below 3rd	Smaller than ~97% of peers. Worth discussing with your pediatrician, especially if it's a new change.
3rd – 15th	Lower end of the typical range. Often perfectly normal, particularly if growth is steady.
15th – 85th	The broad "typical" range where most children fall.
85th – 97th	Higher end of the typical range. Usually normal, especially if consistent.
Above 97th	Larger than ~97% of peers. Worth a conversation with your pediatrician if it's a sudden shift.

Is a high or low percentile bad?

On its own, no. A single percentile is just a snapshot. A baby at the 5th percentile who has always been around the 5th percentile is simply a smaller baby — and likely a healthy one. The numbers that concern pediatricians are the outliers (consistently below the 3rd or above the 97th) and sudden changes.

The trend matters more than the number

Children tend to follow their own curve. A baby tracking steadily along the 25th percentile is usually growing exactly as they should. What's worth attention is "crossing" percentile lines — for example, dropping from the 50th to the 15th over a couple of visits. One measurement never tells the whole story; the pattern over time does.

How percentiles are calculated

Behind the scenes, WHO growth charts use a method called LMS, which converts each measurement into a z-score (how many standard deviations from the median) and then into a percentile. You don't need to do any of that math — our free growth calculator does it instantly using the official WHO data.

Find your baby's percentile

Enter a date of birth, weight, and height to see exactly where your child falls on the WHO charts.

Open the Growth Calculator →

Frequently asked questions

What does the 50th percentile mean for a baby?

The 50th percentile is the median, or middle. A baby at the 50th percentile for weight weighs more than 50% of babies the same age and sex, and less than the other 50%. It doesn't mean perfect or ideal — it simply means average. Healthy babies are found across the whole range.

Is a low percentile bad?

Not on its own. A baby at the 10th percentile can be perfectly healthy, especially if they have always tracked around that line. What matters more is the trend over time. Talk to your pediatrician if your child consistently falls below the 3rd percentile or drops across several percentile lines.

Should my baby always be at the same percentile?

Babies usually track along a similar percentile line over time, but some shifting is normal, particularly in the first 6 months. A steady, large move up or down across multiple percentile lines is worth discussing with your pediatrician.