How Tall Will I Be?

How tall you will be depends mostly on two things you can check today: where you sit on the growth chart for your age, and how tall your parents are. If you stay on the same growth percentile, your adult height will land near that same percentile at age 20. This quiz does that math step by step and gives you a likely range, because the timing of your puberty can move the result up or down.

How the quiz works

1. Your sex and age. Boys and girls grow on different schedules, so each has its own CDC growth curve.
2. Your height. Measure barefoot against a wall in the morning, when you are tallest.
3. Your parents' heights (optional). Real measurements beat guesses.
4. Your result. You get a predicted adult height, a range, and roughly how much growing you may have left.

Behind the scenes, it uses the same method as our height calculator: your percentile on the CDC 2000 stature-for-age charts, projected to age 20, blended with the mid-parental height when you add your parents. The younger you are, the more your parents' heights count; by 16 or 17 your own growth curve does most of the work.

"If I'm 5'5" at 13, how tall will I be?"

Here is how to answer that kind of question yourself. First, find the median (middle) height for your age: at 13 it is 5'1.5" (156 cm) for boys and 5'2" (157 cm) for girls. Then see how far above or below it you are, and assume you keep that position.

Notice the difference: a 5'5" boy at 13 may have around 8 inches left, but a 5'5" girl only about 2. At 13, the median girl has reached about 96% of her adult height, the median boy only about 88%.

Now the important catch. A 13-year-old boy who is 5'5" might be tall for life, or he might be an early bloomer who started puberty sooner and will stop sooner. If his voice has already deepened and his growth is slowing, the lower end of the range (around 5'9.5" to 5'10") is more realistic than 6'1". That's why the quiz shows a range of about ±3 inches at this age.

How tall will I be when I grow up? What decides it

• Genes: about 80% of the differences in height between people comes from inherited gene variants. That's why parents' heights help.
• Puberty timing: decides when you grow. Girls usually hit their growth spurt between 10 and 14; boys grow fastest between about 12 and 15.
• Health and habits: good nutrition, enough sleep and regular activity support normal growth. They help you reach your potential but can't take you past it.

How accurate is a "how tall will I be" test?

The estimate is most useful as a range. It is widest (about ±3 in, or ±7 cm) before and during the growth spurt, and narrows to about an inch or less in the late teens, because most of your growing is already done. Mayo Clinic notes there is no sure way to predict adult height, so be wary of any test that promises an exact number.

The biggest unknown is puberty timing. Late bloomers often get predictions that are too low at first; early bloomers often get predictions that are too high. That is why, if you are in the usual puberty years, the quiz asks whether your growth spurt started earlier or later than your friends': we nudge the projection down by about 0.8 in (2 cm) for early starters and up by the same amount for late starters. Retaking the quiz every 3 to 6 months, with a fresh measurement, makes the estimate better over time. A bone-age X-ray read by a doctor is the only way to narrow it further.

Want to know whether you are still growing at all? Try the Am I Done Growing? quiz, or read about growth spurts.

When to talk to a doctor

Growth worries are worth a checkup if you have grown much less than friends over the past year, if you have dropped down the growth chart, if a boy has no signs of puberty by 14 or a girl by 13, or if your predicted height is far below what your parents' heights suggest. A doctor can look at your growth history and, if needed, order a bone-age X-ray.

The bottom line

Your adult height is mostly written in your genes and your growth curve, and the quiz turns those into a realistic range. Measure carefully, add your parents' heights, and check again in a few months to watch the prediction sharpen.