Height Calculator: How Tall Will You Be, and Your Height Percentile

The mid-parental, or target, height is the simplest height predictor, and the one clinics use beside a growth chart. Here it is for a mother of 5 ft 3 in (160.0 cm) and a father of 5 ft 10 in (177.8 cm).

The 13 cm is the average gap between adult men and women, so the formula moves the mother’s height up to a man’s scale for a son and the father’s down for a daughter. US calculators often use 5 in, the same rule in inches.

Khamis-Roche is a regression equation: predicted adult height = a + b x height + c x weight + d x the parents’ average height, in inches and pounds, with its own a, b, c and d for each sex at every half year from 4 to 17.5. The calculator rounds the age to the nearest half year, as the published table does, converts what you type, and shows the result in both units.

A worked example: a boy of exactly 10, 138.4 cm and 32 kg, whose parents are 162.5 and 177.5 cm. Khamis-Roche predicts 177.3 cm (5 ft 10 in), and 90% of predictions land within 5.3 cm, so 172.0 to 182.7 cm. His mid-parental target is 176.5 cm, and today he is on the 49th percentile of the CDC chart.

In the published table, weight lowers the prediction at every age except a girl’s last half year: at the same height, a heavier child gets a slightly lower number. It is a small term. For the boy above, 10 kg more would take 2.2 cm off.

Its limits are stated in the paper: it was built on white American children without conditions that affect growth. For other children the error may be larger, and a pediatrician with a bone age X-ray can use methods that read it.

A height percentile says what share of children of the same age and sex are shorter. The 50th percentile is the median; the 90th means taller than 90 of 100. The calculator reads it from two charts and shows both: the CDC chart, the US standard from 2 to 20, and the WHO charts, the international standard from birth to 19, which the CDC itself recommends for children under 2.

The two disagree by a few points for most children, because they describe different children: the CDC chart is US children measured from the 1960s to the 1990s, the WHO standards are breastfed children in six countries raised in good conditions, and the WHO reference from 5 to 19 joins them to older US data. Neither is wrong; they are different rulers.

One reading is a snapshot. What a pediatrician looks at is the line over time: a child who keeps their percentile is growing on their own track, whatever the number. A height below the 3rd or above the 97th percentile, or a percentile that keeps falling, is worth raising with a doctor.

The 50th percentile height at each birthday, read from the same tables the calculator uses: the CDC chart first, then the WHO chart. Under 2, the WHO chart is length lying down, which is why the table starts at 2; the WHO reference ends at 19.

The same for girls. On the CDC chart the median girl grows 1.5 cm after 15 and the median boy 1.6 cm after 17: the girls’ column flattens about two years sooner.

For adults, pick “An adult”, then men or women, and enter your height: the calculator places it among US adults of that sex aged 20 and over, measured by the CDC’s NHANES survey from 2015 to 2018 (5,092 men, 5,510 women). Between the printed percentiles it reads along the normal curve; past the 5th and 95th, where the survey prints nothing, it says the number is an estimate.

6 ft is about the 85th percentile for a US man; 5 ft 4 in about the 57th for a US woman. Other countries differ: the tallest and shortest countries’ average heights are about 20 cm or more apart (NCD Risk Factor Collaboration, eLife 2016), and Dutch men born in the late 20th century average over 182.5 cm.

Pick your sex, type your age, height and weight, and your parents’ heights. You get three numbers: your mid-parental target, your Khamis-Roche prediction, and the height you would reach at 20 if you stay on your current CDC percentile. When they agree, that is your likely height. When they do not, the usual reason is timing: a teen who starts puberty early is tall for their age now and gains less later, and a late starter the other way round.

Most growth is done by the late teens: on the CDC chart the median boy grows 1.6 cm from 17 to 20 and the median girl 0.8 cm from 16 to 20.

No method predicts one exact height, and a calculator that shows one without a range is overstating it. Khamis-Roche, the method here that reads the most about the child, had 90% of its predictions were within 5.3 cm for boys and 4.3 cm for girls, averaged over ages 4 to 17.5. The mid-parental target is wider, with Tanner’s range 8.5 cm either side, and it overshoots for the children of very tall or very short parents, who end up closer to average than their parents (Wright and Cheetham, Archives of Disease in Childhood, 1999).

We checked the calculator’s own code against the charts: a child on the CDC median height and weight, with parents at the US median heights, gets a Khamis-Roche prediction within 1.1 cm of the CDC median at 20 for boys and 1.7 cm for girls, at every half year from 4 to 17.5. That shows the method and the charts agree; it is not a test on real children grown up, which no public data allows.

One inch is exactly 2.54 cm, and one foot 30.48 cm. Common heights from 4 ft 10 in to 6 ft 6 in:

Once the growth plates close, height is set. What still changes is how tall you read: posture first, since a forward head and rounded shoulders lower the top of your head, then the fit and proportions of your clothes, and body fat, which sets how long your neck and how sharp your jaw line read.

To see a height difference rather than a number, put two heights side by side in the height comparison chart. For what your build carries at your height, the FFMI calculator measures fat-free mass against height, the number that changes with training.