Growth calculator: weight and height percentiles, birth to 19

Check the growth

Enter the age in years and months, the sex, then weight or height — no need for both; whichever you have to hand. Height works from birth to nineteen years; weight to ten.

What to enter and what the number means

The tool runs on the World Health Organization growth charts — the same ones printed in your doctor's file and on the back of the immunisation card. The answer is a percentile.

The 50th percentile is the midpoint: out of a hundred children, about fifty measure less than yours and fifty more. The 15th percentile means fifteen measure less, eighty-five more.

Weight stops at ten because WHO stops publishing weight-for-age there. It is not an omission. Once puberty begins, two healthy children of the same age and weight can be at completely different stages of growing, so weight on its own stops carrying a clear meaning and height and BMI take over.

Two different charts meet at five years

Under five, the tool uses the WHO Child Growth Standards, published in 2006. These are prescriptive: they were built by following healthy, well-nourished, predominantly breastfed children in six countries — Brazil, Ghana, India, Norway, Oman and the United States — and they describe how children grow when nothing is holding them back.

That study produced one of the more useful findings in child health: given a good start, young children of every ethnicity grow much alike. The differences between countries are overwhelmingly nutrition, infection and care rather than genetics. Which is why the same chart is right for an Indian under-five as for a Norwegian one, and why building a chart from how Indian children actually grow would quietly write the country's undernutrition into the definition of normal.

From five to nineteen, the tool uses the WHO 2007 growth reference. This one is descriptive rather than prescriptive: it was reconstructed from older survey data and shows how a reference population did grow, not how children ideally should. It is the international standard for this age group and it joins smoothly onto the under-five chart, but a percentile here carries a little less weight than one below five.

Above five, genuine population differences do open up, largely through the timing of puberty. The Indian Academy of Pediatrics published charts for Indian children aged 5 to 18 in 2015, and many Indian paediatricians use those. If your doctor's percentile differs from ours for an older child, this is the likely reason, and it is worth asking which chart they are reading.

What a percentile is — and isn't

Percentiles are not marks. The 90th is not 'better' than the 15th. Both are on the chart, and both can be perfectly healthy.

The large majority of healthy children track somewhere between the 3rd and 97th lines. A child moving steadily along the 15th line is most likely simply built that way — small parents tend to have children on the lower lines, as expected.

And two children's percentiles are not for comparing. A growth chart is one child measured against their own past, not a race against the neighbour's baby.

Not a dot — the shape of the line

The most important sentence on this page: a single measurement tells you almost nothing. A growth chart is a line over time, and the meaning is in the line's shape.

A baby steady on the 15th line for six months is fine. A baby sliding from the 90th to the 50th to the 25th — even while still 'in the normal range' — is worth checking.

So this tool answers with one number, but the real verdict lives in your doctor's file, where all the past visits' dots are joined. Use this alongside that file, not instead of it.

The errors that sneak into measurements

A home weighing with clothes and a nappy reads three hundred to five hundred grams heavy. Clinics weigh babies undressed, which is why home and clinic numbers never match.

Children under two are measured lying down, not standing, and a lying measurement reads about half to one centimetre longer than a standing one. Measuring the same way every time matters more than the number itself.

Count the age precisely. At young ages a single month's error moves the percentile a long way: a three-month-old's weight read on the four-month row will worry you for nothing. For older children a month matters less, except around the puberty growth spurt, where it matters again.

Head circumference — the third measurement

At every visit the doctor measures three things: weight, height, head circumference. The third gets the least attention and says the most in the first two years, because head growth is brain growth, directly.

At birth the head measures about thirty-five centimetres and grows twelve more in the first year, half of that in the first three or four months. It isn't in this tool because it's hard to measure correctly at home; the tape must cross above the eyebrows and around the widest point at the back.

But it's in your file, and worth looking at there. A circumference suddenly crossing lines upward, or stalling, are both same-week conversations with the doctor.

What actually helps — and when to see the doctor

Exclusive breastfeeding to six months, then home-cooked solids introduced and built up — growth needs little more than that in the early years. Preventing repeated diarrhoea and chest infections is the other half.

Skip the 'weight gain' powders and appetite syrups unless a doctor prescribes them. Some children are simply lean, and need nothing.

See the doctor if: weight or height crosses two lines downward on the chart, weight gain stalls, birth weight isn't regained by two weeks, or a flat line comes with a listless baby. In an older child, growing less than about four to five centimetres a year through mid-childhood is the equivalent signal. Catching these early is what the regular weigh-ins — including the monthly anganwadi one — are for.

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