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Baby percentile calculator

Enter your baby's sex, age and measurements. We compare them with the WHO growth standards.

WHO percentiles

Enter a measurement to see its percentile.

Birth to 24 months. For babies born early, ask your doctor how to read percentiles.

How it works

We use the WHO growth standards for children from birth to 24 months, which the CDC recommends in the US. Each measurement is compared with babies of the same sex and age using the WHO LMS method: z = ((measurement / M)^L minus 1) / (L x S), where L, M and S come from the WHO tables for that age (we interpolate between months). The z-score becomes a percentile.

Measure carefully: weigh without clothes or a diaper if you can, and measure length lying down. Percentiles from home measurements are a guide; your doctor's measurements are the ones that count.

Sources: CDC, WHO growth standards data files (birth to 24 months); CDC, "Using WHO Growth Standard Charts".

Frequently asked questions

What percentile should my baby be in?

There is no single right percentile. Anywhere between the 2nd and 98th falls within the WHO standards; steady growth along a line matters most.

Which growth chart does my pediatrician use?

For children under 2 in the US, the CDC recommends the WHO growth standards, the same data this calculator uses.

Checkup by checkup

Your child, checkup by checkup

One short email at each CDC milestone age, from 2 months to 5 years: what most children do by then, a checklist to bring to the checkup and when to talk to your doctor.

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