Growth and weight percentiles in Happy Baby

Growth and weight percentiles are a tool doctors use to track a baby’s physical development compared with other children of the same age. They’re based on large studies (such as WHO growth charts) that collected height, weight, and head circumference measurements from thousands of children.

Once you enter your baby's height and weight in the trends section, you can follow the progress over time.

What does “percentile” mean?

• A percentile shows the percentage of children who fall below a certain measurement.

  • 50th percentile → right at the average.

  • 5th percentile → 5% of children weigh/measure less, 95% more.

  • 95th percentile →95% of children weigh/measure less, 5% mor

So the percentile is not a grade or score and doesn’t mean “good” or “bad” – it’s simply a way of showing where a child falls compared with others.

Typical patterns in the first year

• Weight: Babies gain weight rapidly in the first months. A healthy baby can be on the 10th percentile or the 90th – both are normal. What matters is that they continue along their own growth curve.

• Length/height: Same idea – the trend matters more than the absolute number.

• Head circumference: Also measured regularly, since it reflects brain growth.

Why doctors use percentiles

• To see if the baby is growing steadily.

• To spot sudden changes, for example if a baby drops from a higher percentile line to a much lower one.

• To check whether growth, nutrition, and overall health are on track.

Key points:

• Some babies are naturally smaller/lighter or bigger/heavier – that’s usually completely normal.

• The most important thing is the child’s own growth trajectory over time, not any single measurement.