This height calculator predicts adult height for boys and girls aged 2 to 20 from their age, sex and current height, plus both parents' heights if you have them. It finds where the child sits on the CDC growth charts today, projects that position to age 20, and blends it with the height the parents' genes point to. You get a predicted adult height and a likely range, not a promise.
How to use the height calculator
- Measure first. Stand barefoot against a wall, heels, back and head touching it, and mark the top of the head with a flat book. Measure in the morning, when you are tallest.
- Enter age, sex and height. Use your exact age; during puberty, a few months make a difference.
- Add both parents' heights if you can. Measured heights work better than remembered ones; doctors are advised to measure parents rather than ask.
- Read the result and the range. The middle number is the best estimate; the range shows how far real heights commonly land from it.
How the height prediction works
1. Your growth curve (CDC percentile projection)
We use the CDC 2000 stature-for-age growth charts, which cover ages 2 to 20. From the CDC's published LMS tables, we calculate the child's z-score, a number that says how far above or below the median they are for their exact age and sex. We then assume they keep the same position and read off the matching height at age 20.
Example: a 14-year-old boy who is 5'4.5" (163.5 cm) is right at the median for his age. Keeping that position puts him near the median adult height on the chart, about 5'9.5" (176 cm).
2. Your parents' heights (mid-parental target)
Height runs in families: about 80% of the differences in height between people comes from inherited gene variants. So we also compute the Tanner mid-parental target height: for boys, (father + mother + 5 in) ÷ 2; for girls, (father + mother − 5 in) ÷ 2. You can try it on its own with the mid-parental height calculator.
3. Blending the two
When parents' heights are given, the calculator combines both estimates. The older the child, the more the result relies on their own growth curve, because a teen's current height says much more about adult height than a toddler's does.
| Age | Weight on child's growth curve | Weight on parents' heights |
|---|---|---|
| 2–9 | About half | About half |
| 10–15 (boys), 10–13 (girls) | About 55–85% | About 15–45% |
| Boys 16–17, girls 14–15 | 90% or more | 10% or less |
Height calculator for boys vs. girls
Boys and girls get separate CDC curves because they grow on different schedules. At 13, the median boy and girl are almost the same height, about 5'1.5" (156 cm) and 5'2" (157 cm). But the girl has already reached about 96% of her adult height, while the boy is at about 88% and still has his biggest growth spurt ahead. That's why the same height at the same age can lead to very different predictions.
How accurate are height predictors?
The range we show is roughly ±3 in (±7 cm) in childhood and early puberty, narrowing to about an inch or less in the late teens, as most growth is already done.
The biggest source of error is puberty timing. An early bloomer looks tall at 12 or 13, then stops growing sooner. A late bloomer looks short, then catches up. Any method based on height alone will misjudge both for a while.
Other prediction methods exist:
- Khamis-Roche uses height, weight and parents' heights. It was developed from a study of white American children in Ohio, which limits who it fits. We don't use it.
- Bayley-Pinneau uses bone age from a hand and wrist X-ray, so it needs a doctor.
- "Double the height at age 2" (18 months for girls) is a quick rule of thumb.
Mayo Clinic is clear that there is no sure way to predict adult height. The only way to narrow the estimate beyond what any online tool can do is a bone-age X-ray read by a doctor.
What affects the result
- Genetics: the biggest factor.
- Puberty timing: shifts when you grow, and sometimes how much.
- Health: chronic illness, hormone problems and some medicines can slow growth.
- Nutrition and sleep: they help you reach your genetic potential while you are still growing; they can't push you past it.
For a step-by-step version made for teens, try the How Tall Will I Be? quiz. To see how your height compares today, use the height percentile calculator. The full math is on our methodology page.
When to check with a doctor
See a doctor if growth has slowed or stopped early, if a child drops across percentile lines on the growth chart, if there are no signs of puberty by about 14 in boys or 13 in girls, or if the prediction is far below what the parents' heights suggest. These are reasons for a proper growth evaluation, not something a calculator can settle.
Frequently asked questions
How accurate is a height calculator?
For a healthy child or teen, the true adult height usually falls inside the range we show, roughly 3 inches either way in childhood and about an inch or less near the end of growth. No calculator can know in advance when puberty will start, which is the biggest source of error. A bone-age X-ray read by a doctor is the only way to narrow the estimate further.
What age does the height calculator work for?
From age 2 to 20, because it uses the CDC stature-for-age charts, which cover those ages. After 20, height has stopped changing for almost everyone, so the calculator simply shows your current height.
Is the 'double your height at age 2' rule accurate?
It is a quick rule of thumb, not a precise method. Mayo Clinic describes doubling a boy's height at age 2, or a girl's at 18 months, as one rough way to guess adult height. A calculator that uses growth charts and parents' heights gives a more complete picture.
Why did my predicted height change when I re-measured?
Because the prediction follows your growth curve. If you grew faster or slower than the average teen since your last measurement, your percentile moved and so did the projection. That is normal, especially during puberty, and it is why re-measuring every few months helps.
Can a height calculator tell if I'm a late bloomer?
Not on its own. A late bloomer looks short for their age until their growth spurt arrives, so any calculator based on height alone may underestimate them for a while. Signs of puberty, your parents' growth history and, if needed, a bone-age X-ray help sort this out.
Sources
- Growth Charts: Data Table of Stature-for-age Charts (LMS parameters) — CDC
- Height Potential: A Child's Target Height Based on Midparental Height — MSD Manuals (Merck Manual Professional)
- Child growth: Can you predict adult height? — Mayo Clinic
- Predicting adult stature without using skeletal age: the Khamis-Roche method (Pediatrics, 1994) — PubMed
- Evaluation of Short and Tall Stature in Children — American Family Physician (AAFP)
- Is height determined by genetics? — MedlinePlus Genetics (NIH)
- X-Ray Exam: Bone Age Study — Nemours KidsHealth
Updated 2026-11-05. How our calculators work · Editorial policy