Is a baby measured lying down or standing?

Lying down until two, standing after. The tables switch at the same point, so a measurement taken the other way reads against the wrong column — worth about 14.6 percentile points at that age.

Which chart applies to a baby in the US or the UK?

WHO’s. Both countries read WHO below two and switch to their own charts after — so under two the medians here are identical whichever of the three you pick.

Can a newborn’s weight be given a percentile?

Yes. The reference starts at 0 months, so a birth weight has a percentile like any other measurement. It describes position in the reference population, not a verdict on the baby.

Calculators

Infant growth percentile calculator

A baby’s length and weight as percentiles — centiles, in British usage — from birth to two, under WHO 2006/2007. Below two this is the same chart everywhere: the US and UK read WHO at this age.

Fill in the fields to see the position

How to read this number

Below two a baby is measured lying down, and that measurement is called length rather than height. It is not a wording difference: the same child measures about 0.67 cm shorter standing than lying, and WHO builds that step into the table at the second birthday. Reading a lying-down measurement against the standing table moves the percentile by about 14.6 points.

The tables here for this age are WHO 2006, built from children raised in good conditions and fed as recommended — it describes how healthy children grow, not how one population happened to grow. That is why so many countries adopt it below two rather than publishing their own.

Birth is in the table too. A weight at 0 months gives a newborn weight percentile against the same reference, which is what a maternity discharge note is usually quoting.

The standard behind it

This calculator uses WHO Child Growth Standards (2006) · WHO Growth Reference (2007)’s LMS parameters. Ages 0–5 use the 2006 Child Growth Standards and 5–19 the 2007 growth reference; the two join at five.

The source tables are taken straight from who.int, data version 2026-08-25. Ages beyond what a standard covers are never extrapolated — the page says there is nothing there.

Common questions

Is a baby measured lying down or standing?: Lying down until two, standing after. The tables switch at the same point, so a measurement taken the other way reads against the wrong column — worth about 14.6 percentile points at that age.
Which chart applies to a baby in the US or the UK?: WHO’s. Both countries read WHO below two and switch to their own charts after — so under two the medians here are identical whichever of the three you pick.
Can a newborn’s weight be given a percentile?: Yes. The reference starts at 0 months, so a birth weight has a percentile like any other measurement. It describes position in the reference population, not a verdict on the baby.