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Baby Growth Percentile Calculator

Weight, length and head circumference percentiles from the WHO Child Growth Standards, 0-24 months.

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Open Baby Growth Percentile Calculator and you get an answer straight away, with no account to create. You will find it under Pregnancy & baby, with Baby Milk Intake Calculator and Child BMI Percentile Calculator for the neighbouring cases.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Baby Growth Percentile Calculator do?

Weight, length and head circumference percentiles from the WHO Child Growth Standards, 0-24 months.

When would I actually use this?

Placing a pregnancy on the calendar: the estimated due date, the current week, and when the usual appointments and screenings fall.

What is the most common mistake?

Reading the due date as a deadline. It is a median: fewer than one birth in twenty happens on it, and a normal term spans several weeks around it.

How is Baby Growth Percentile Calculator different from Baby Milk Intake Calculator?

They sit next to each other but answer different questions: Baby Milk Intake Calculator is the one to open when you need it to bottle volumes per feed and per day by your baby's weight and age, with the feeding interval. Pick whichever matches what you're starting from — both are free.

Is there a tool for the next step?

Child BMI Percentile Calculator is the closest one after this: BMI-for-age percentile on the CDC reference, ages 2-20 — the percentile, not the BMI, is what counts for a child.

What else is worth having open alongside it?

Height Percentile Calculator and Gestational Age Calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

The WHO Child Growth Standards for 0–24 months — weight-for-age, length-for-age and head-circumference-for-age — used as the LMS parameters WHO publishes, at its own monthly age points, not a curve redrawn by eye. A percentile is a position in that reference population, not a verdict: it is the trend across visits, and the child's own line, that a paediatrician reads.

Further reading

All guides →
ExplainerBaby Growth, and What Crossing Centiles Actually MeansThe WHO infant standard is prescriptive: it was built from healthy breastfed babies and describes how infants should grow. National references describe how they did grow. In the first year the two disagree by enough to move the same baby forty percentile points, with no change in the baby. Here is the size of the gap, and what the published thresholds for concern actually say.ExplainerHow Much Milk Does a Baby Need? The Rule of Thumb and Its LimitsA formula-fed baby takes roughly 2.3 fl oz per pound of body weight per day in the first months, split across the day's feeds. Here is the table by age and weight, why breastfed babies are not measured this way, and the signs that outrank any number.ExplainerGrowth Percentiles: What a Child's Centile Really MeansA centile ranks a child against a reference population — it is not a grade, and one reading says almost nothing. Here is the LMS arithmetic behind the number, and why the same boy is on the 90th centile on one chart and the 85th on another.ExplainerHow Tall Will a Child Be? The Arithmetic Is Easy; the Error Bar Is the StoryAverage the parents' heights, shift by a sex constant, and you have a target height. The honest part is what comes next: the published prediction interval is about ±4 inches, wide enough to cover most of the adult population. Here is the formula, the interval, why bone age does better, and why children keep out-growing the target.ExplainerWhere a Percentile Comes From: Which Population, Measured WhenA percentile is a rank against a reference population, so the first question is never the arithmetic — it is which population, measured when. The same 5'11" man is the 38th percentile in one national dataset and the 86th in another, and the 91st against a reference of people born a century ago. Here is why, and what a z-score adds.ExplainerIVF Dating Is the One Case Where the Date Is Actually KnownEvery other pregnancy is dated from an estimate. After IVF, fertilisation is timed to the hour, so gestational age is arithmetic: 266 days from fertilisation, minus the embryo's age at transfer. Here is the derivation for day-3, day-5 and day-6 embryos, why frozen and fresh transfers use the same rule, why an early scan rarely moves an IVF date, and what the two-week offset on a scan report means.