Baby growth percentile calculator

How to read the result

A percentile compares your baby with healthy babies of the same age and sex. The 40th percentile for weight means about 40 out of 100 babies weigh less. No single number is good or bad. What pediatricians care about is the trend: babies tend to follow their own curve, and a big change across percentile lines is worth a conversation.

Tracking growth over time

TallyTot saves every measurement and shows the WHO percentile next to it, and the doctor-visit summary includes the latest growth. See the growth tracker.

FAQ

What percentile should my baby be in?

There is no “right” percentile. A baby on the 10th percentile can be just as healthy as one on the 90th. Pediatricians look at whether your baby follows their own curve over time; a sharp drop or jump across two major percentile lines is what prompts a closer look.

What does 50th percentile mean?

Half of babies of the same age and sex measure less, and half measure more. The 25th percentile means about 25 out of 100 measure less.

Why does this use WHO charts instead of CDC charts?

The CDC and AAP recommend the WHO Child Growth Standards for all babies under 2 in the US. They describe how healthy breastfed babies grow, and are what your pediatrician plots.

Is a home weigh-in accurate enough?

Bathroom-scale weigh-ins (holding baby, minus your weight) can be off by half a pound or more, and length is hard to measure at home. Use the numbers from your pediatrician’s office when you can.

Data: WHO Child Growth Standards (LMS parameters, 0–24 months), as published in the CDC’s WHO data files. Use of these data does not imply CDC or WHO endorsement. For information only; not medical advice.