Baby growth percentile calculator
See where your baby’s weight, length, or head circumference sits on the WHO growth charts (0–24 months) — and, more importantly, what that number does and doesn’t mean.
Not sure of the age in months? Use the baby age calculator.
Enter a measurement to see the percentile.
What a percentile actually means
The 42nd percentile means about 42 of every 100 healthy babies of the same age and sex measure less. That’s all it means. The 50th is not a grade, and higher is not better — a healthy child can track along the 10th line their whole childhood, and many do.
The trend matters more than the number
A single measurement is a snapshot; growth is a film. What paediatricians actually look at is the curve across checkups — whether your baby is roughly following their own line. This calculator helps you decode one point on that film; it can’t see the film itself.
How babies are measured
Clinics weigh babies naked and measure length lying down until age two — so a home measurement with clothes on, or standing height, can easily sit a few percentiles away from the clinic number. Treat home numbers as rough.
When to talk to your paediatrician
Below the 3rd or above the 97th percentile, a curve that crosses two major percentile lines between checkups, or simply a gut feeling that something’s off — all good reasons for a conversation. None of them is a diagnosis; they’re the chart’s way of saying “worth a look”.
Frequently asked questions
What percentile should my baby be?
There’s no “should”. Healthy babies run the whole range, from the 3rd percentile to the 97th — the chart describes variety, not a target. What matters is that your baby roughly follows their own curve over time.
Is the 50th percentile the goal?
No — it’s just the middle. A baby on the 15th percentile is not “worse” than one on the 70th, any more than a shorter adult is worse than a taller one.
My baby dropped percentiles — should I worry?
Small wobbles between checkups are common, especially around growth spurts and illness. Crossing two of the major percentile lines on the chart is the conventional cue for a closer look — that’s a conversation for your paediatrician, who can see the whole curve.
Why does this calculator use WHO rather than CDC charts?
For children under 2, the CDC itself recommends the WHO growth standards, which describe how healthy, predominantly breastfed babies grow in optimal conditions. The CDC references are typically used from age 2 on.
Are boys’ and girls’ charts really different?
Yes — boys are, on average, slightly heavier and longer at the same age, so the WHO publishes separate tables by sex. The differences are small but real enough that percentiles are always read against the matching table. If a boy-or-girl label doesn’t fit your family’s situation, your paediatrician can advise which chart to use.
Percentiles computed with the LMS method from the World Health Organization Child Growth Standards (tables retrieved 17 July 2026). This tool is general information, not medical advice or a diagnosis — growth is properly assessed only by health professionals, over time. See also the baby milestones guide and sleep needs by age.