A LITTLE SCIENCE. A BIG QUESTION.
How tall will you be?
A few measurements. A research-based estimate of your adult height.
BEHIND THE NUMBER
Growth, with a little context.
A simple equation. Clear limitations.
Built on the Khamis–Roche method
For ages 4–17.5, we combine current height, weight and the average of both parents’ heights with age- and sex-specific coefficients. We interpolate between half-year ages for decimal inputs.
How the calculation works
Adult height = a + b × height + c × weight + d × average parent height
The equation runs in inches and pounds, then converts back to centimetres. The coefficients change with age and sex. Interpolation is an implementation choice, not an independently validated extension of the study.
Below age 4, the fallback is (mother’s height + father’s height ± 13 cm) ÷ 2: add 13 for males, subtract 13 for females. Above 17.5, we show current height without extrapolating the child equation. At 20 and older, that value stays unchanged.
How accurate is the estimate?
The original model was developed from 433 white American children without growth-affecting conditions. It may be less accurate for other populations or unusual growth patterns. The approximate ranges use average error bounds of ±5.3 cm for males and ±4.3 cm for females; they are not age-specific intervals.
Use measured heights, without shoes. Weight is a statistical input; changing your weight does not cause the predicted change in height. A clinician can assess growth over time and bone age when needed.
What does the growth timing option do?
It is optional, it starts on Average, and on Average it changes nothing at all: the number you get is the plain Khamis–Roche estimate. It is our own addition, not part of the study.
Pick Late bloomer or Early bloomer and we read your height against a maturity 0.6 years younger or older than your actual age, using the same CDC median curve as the chart above. A late maturer has reached less of their adult height than their years suggest, so more of it is still ahead; an early maturer has already spent more of theirs. The difference between those two readings is what we add or subtract.
The idea is borrowed from the Bayley–Pinneau method, which switches between accelerated, average and delayed tables when a bone-age X-ray differs from chronological age by more than a year. We are not doing that. We use a self-description instead of a bone age, and a deliberately smaller shift because of it. The adjustment applies only through puberty, fades to nothing at either end of it, and is capped at 7 cm. Treat it as a what-if, not a second opinion.