Child Height Percentile Calculator

The most inherited thing about your child

Of everything you can measure about a child, height is the one where the answer was largely decided before they were born.

Height is among the most heritable traits we have. Estimates from twin and family studies generally land around 80 percent, meaning most of the variation in how tall people end up is explained by their genes rather than anything that happened to them. Not all of it: nutrition matters, illness matters, and populations have grown taller across generations as conditions improved, which proves the environment has a say. But the say is a minority share, and in a well-fed child in a healthy home it is a small minority share.

This is worth internalising before you read the number this tool gave you, because it reframes what the number is. Your child's height percentile is, to a large extent, a readout of their ancestry. A child at the 15th percentile with two short parents is not underperforming. They are doing exactly what their genes specified. There is no version of that child at the 60th percentile that better nutrition would have produced.

Which makes the interesting question not "what percentile is my child on" but "is my child on the percentile you would expect, given who they came from". That is a question you can actually answer, and the next section shows you how.

Work out roughly where they are heading

There is a rough estimate clinicians use called mid-parental height, and it is simple enough to do on the back of an envelope. It will not be exact. It gives you the neighbourhood.

Take both parents' heights in centimetres, then:

For a boy: (mother's height + father's height + 13) ÷ 2
For a girl: (mother's height + father's height − 13) ÷ 2

The 13 centimetres is roughly the average adult height difference between men and women, added or subtracted so that the sum is comparing like with like.

So a mother of 162 cm and a father of 178 cm:

Son: (162 + 178 + 13) ÷ 2 = 176.5 cm
Daughter: (162 + 178 − 13) ÷ 2 = 163.5 cm

Treat those as a centre point with a fair margin either side, in the region of 8 to 10 cm, because two parents' heights cannot capture everything in a family. Grandparents are in there too, and a tall recessive streak can skip a generation and surprise everybody.

Now the useful move: compare that estimate with the percentile this tool just gave you. If your child is tracking somewhere near where the family arithmetic points, that is the reassuring answer, whatever the number is. If your child is tracking a long way from it, in either direction, that is a more interesting observation than the percentile alone, and it is a genuinely good thing to mention to a doctor. Our Height Calculator works this estimate properly.

Children pick a channel and stay in it

Here is the thing that makes growth charts work, and it is one of the quiet marvels of human development.

Children do not wander around the chart. In the first couple of years they settle onto a percentile line, and then they follow it, for years, with remarkable fidelity. A child who is on the 30th at three is very likely to be near the 30th at nine. It is as though each child has a lane and drives in it.

This is why a single percentile is worth so much less than a series of them, and why a doctor with two years of dots on a chart knows more than this calculator ever can. The lane is the information. Your child's lane being low is not a finding. Your child changing lanes is.

The tracking is also robust to interruptions, which is the genuinely impressive part. A child who is properly ill for a while may fall off their line, and then, once well, will often grow unusually fast until they arrive back at the line they were on before, and then resume the normal pace. It has a name, catch-up growth, and nobody fully understands the mechanism. Somewhere in there, a child's body appears to know where it was supposed to be.

Two honest exceptions, so you are not alarmed by normal things. The first is the settling period in the first two years, when a baby is moving from the size the pregnancy made them toward the size their own genes intend, and some crossing of lines is expected. The second is puberty, which wrecks the whole picture for a few years: children who start early shoot up the percentiles and then stop, and children who start late sink down them and then catch up. A thirteen-year-old boy's height percentile is measuring the timing of his puberty at least as much as his eventual height, which is why a late developer at the 10th percentile at fourteen may be at the 40th at eighteen.

Whose children is your child being compared to?

A percentile is a comparison, so it is fair to ask what your child is being compared against. The honest answer has an asterisk on it.

This tool uses the CDC growth charts, which cover ages two to twenty and are the ones the CDC and the American Academy of Pediatrics recommend for that age range. They are built from surveys of American children measured between 1963 and 1994.

Note the word: a reference, not a standard. The distinction is the CDC's own and it matters. A standard is prescriptive and says how children should grow given good conditions. A reference is descriptive and says how a particular group of children actually did grow, whatever their conditions were. The WHO charts used by our Baby Growth Percentile Calculator for the under-fives are a standard. These are a reference.

For height this distinction is less troubling than it is for weight, which is worth saying. A descriptive sample of a well-fed population is a perfectly reasonable yardstick for stature, and heights did not shift dramatically across the survey period. Your child is being compared against several decades of American children, which is a large and reasonable comparison group, even if it is not your country and not this decade.

The place it does bite is ancestry. Average adult height genuinely varies between populations, by rather more than most people expect. A chart built on an American sample is not perfectly calibrated for a child whose family is from somewhere with a different average, and it will place them lower or higher than a chart built on their own population would. This does not make the number useless. It makes it a comparison against American children of the late twentieth century, which is what it is, and it is one more reason the family arithmetic above is the better sanity check.

Measuring a child without lying to yourself

Height sounds like the easy measurement and it is not. Small errors move percentiles, and the errors are not random: they nearly all make a child look taller.

• Shoes off, socks fine. Obvious, and skipped constantly.
• Heels, bottom and shoulder blades against the wall, feet together and flat.
• Head level. The line from ear to eye socket should be horizontal. A child tipping their chin up to be helpful adds a centimetre.
• A flat object on the head, at a right angle to the wall. A book, not a hand. Hands press down and tip.
• Same time of day. People are genuinely taller in the morning, by up to a centimetre, because the discs in your spine compress across the day. Measure a child before school one month and after football the next and you have invented a growth problem.
• Under two, measure length lying down, which is a two-person job and a different measurement from standing height.

Get the age right too. This chart works in months, and a child's height changes fast enough that being a few months out matters, particularly in the early years.

What actually prompts a doctor to look twice

To be clear about which things are signals and which are just numbers.

Worth asking about:

• Crossing lines. A child drifting steadily downward through percentiles over a year or more, having previously tracked a lane. This is the main one.
• A big gap from the family estimate. A child tracking far below what both parents' heights would predict.
• Growth that has slowed or stopped when it should not have. A child who has not needed new trousers in eighteen months is telling you something.
• Height and weight moving apart, particularly a child gaining weight while height stalls.
• Anything alongside it: tiredness, poor appetite, digestive symptoms, or a child who seems unwell in themselves.

Not signals on their own: a low percentile that has always been low; a child shorter than their friends; a child shorter than a sibling was at the same age; a late developer in a class of early ones.

If something does need looking at, the good news is that the causes worth finding are findable, and most are treatable, and finding them earlier is better than finding them later. That is the entire reason charts exist. They are not there to rank children. They are there so that the small number who need help are spotted, and so that everyone else can be reassured and left alone.

Questions people ask

My child is on a low percentile. Will they be short?

Probably shorter than average, yes, since children tend to track their lane. Whether that is a problem depends entirely on whether it matches the family. A short child of short parents is doing exactly what you would expect.

Can I make my child taller?

Not meaningfully, beyond making sure they are well fed, well slept and well. Height is roughly 80 percent genetic, and once nutrition is adequate there is no lever left to pull. Nothing sold on the internet changes this.

Should my child be at the 50th percentile?

No. The 50th is the middle of the distribution, not a target. Half of all healthy children are below it, necessarily. The right percentile for your child is the one they consistently track.

My teenager has dropped percentiles. Should I worry?

Around puberty, usually not. Timing dominates height percentiles through those years, and a late developer will sink before catching up. Sustained crossing outside the puberty window is more worth asking about.

Can I use this for a baby?

No, this chart starts at two years. For younger children use our Baby Growth Percentile Calculator, which uses the WHO standards recommended for that age.

References

Where the figures come from. The charts behind this tool are the CDC growth references for ages 2 to 20, which the CDC and the American Academy of Pediatrics recommend for that age range. The CDC also sets out the distinction between a prescriptive standard and a descriptive reference, and the recommendation to use the WHO standards below two years, which was published formally by Grummer-Strawn and colleagues.

1. Centers for Disease Control and Prevention. Growth charts: recommendations and rationale. https://www.cdc.gov/growth-chart-training/hcp/using-growth-charts/recommendations-and-rationale.html
2. Grummer-Strawn LM, Reinold C, Krebs NF. Use of World Health Organization and CDC growth charts for children aged 0-59 months in the United States. MMWR Recommendations and Reports. 2010;59(RR-9):1-15. https://pubmed.ncbi.nlm.nih.gov/20829749/
3. Centers for Disease Control and Prevention. WHO Child Growth Standards. https://www.cdc.gov/growth-chart-training/hcp/training/who-child-growth-standards-training.html