I have added another free tool, a child growth percentile calculator built on the same World Health Organization growth standards that South Africa’s Road to Health book uses.
The clinic plots your baby’s weight, length and head size in the little book, but the curves can be hard to read between visits. This tool turns a measurement into a plain percentile. Enter your child’s sex, date of birth and what you measured, weight, height or head circumference, and it tells you which percentile they are on and whether that sits in the healthy range, for any age from birth to five years.
Just as important, it explains what the number means, because a low or high percentile is so often misread. It shows where your child sits between the 3rd and 97th lines, gives the median for their age to compare against, and gently flags when a reading is far enough outside the usual range to be worth showing your nurse.
Try it here: Child Growth Percentile Calculator South Africa
The honest part matters here. A percentile is a ranking, not a mark out of a hundred, so the 20th percentile is perfectly healthy, it just means the child is smaller than most. One reading says little on its own, what counts is the line your child follows over time, which is exactly what the Road to Health book tracks. It is general information, not medical advice, so always take the book to the clinic and ask if you are worried.
If you have the Road to Health book, does the percentile here match where your clinic plots your little one?