Predicted Adult Height Calculator

Use the Predicted Adult Height Calculator

This predicted adult height calculator estimates how tall a child will be as an adult using current height, age, sex, and parental height for boys and girls.

How to Use Predicted Adult Height Calculator

1. Step 1: Choose sex and units

   Select boy or girl, then pick centimeters or feet and inches. Prediction curves differ by sex, so this choice matters.

2. Step 2: Enter age and current height

   Type your child's age in years and months and their current standing height, measured without shoes against a wall.

3. Step 3: Add both parents' heights (optional)

   Enter the mother's and father's heights to blend the genetic mid-parental target into the estimate. Leave them blank for a percentile-only prediction.

4. Step 4: Read the prediction and range

   See the predicted adult height, the likely range around it, and how your child's current percentile projects to adulthood.

5. Step 5: Check the reference table

   Compare predicted adult heights across the 10th to 90th percentiles for your child's age to see how sensitive the result is.

Key Features

• Predicts adult height from a child's current height, age, and sex
• Blends growth-chart percentile tracking with the mid-parental genetic target
• Works for boys and girls, ages 2 to 18
• Shows a likely height range, not just a single number
• Metric and imperial units with instant, private results

Understanding Results

Formula

The prediction blends two estimates. The trajectory estimate reads your child's current height-for-age z-score and projects it onto the adult height distribution: predicted = adult median + z × adult SD, using an adult median of ~176.8 cm for men and ~162.9 cm for women. The genetic estimate is the Tanner mid-parental height: (mother + father) ÷ 2, then +6.5 cm for a boy or −6.5 cm for a girl. The two are combined with an age-weighted average — the child's own trajectory rises from about 45% of the weight at age 4 to 90% by age 16, since the percentile channel becomes more fixed as growth finishes.

Reference Ranges & Interpretation

The predicted figure is the center of a range, not a fixed value. The likely band spans about ±9 cm at age 4 and narrows to under ±5 cm by the mid-teens. Anchor points help: the average US adult man is ~176 cm (5'10") and woman ~163 cm (5'4"), and roughly two-thirds of adults fall within 7 cm of the average for their sex. A prediction near those medians sits close to the 50th percentile; a prediction 15 cm above the median is near the 97th.

Assumptions & Limitations

The calculator assumes typical, healthy growth and average puberty timing. It cannot see an early or delayed growth spurt, and it is least accurate for children under 4 or those whose height crosses percentile channels. It does not use a bone-age X-ray, which is the clinical gold standard for atypical growth. Treat the result as an educational estimate: if your child sits below the 3rd percentile, is drifting across percentile lines, or you have any concern about their growth, share the growth chart with a pediatrician rather than relying on this number.

Complete Guide: Predicted Adult Height Calculator

A predicted adult height calculator answers the question nearly every parent asks at some point: how tall will my child be? Genetics sets roughly 80% of the answer, which is why height clusters so strongly in families. The other 20% comes from nutrition, sleep, general health, and the timing of puberty. No formula can see a growth spurt that hasn't happened yet, but a good estimate uses two clues that are already visible today: where your child sits on the growth chart right now, and how tall the two parents are.

This guide explains the four prediction methods clinicians and researchers actually use, shows the math behind the estimate on this page, and walks through a full worked example. The goal is not just a number, but knowing how much to trust it.

Four Ways to Predict a Child's Adult Height

Height prediction is not one formula. Four distinct approaches trade accuracy for convenience in different ways. The table below compares them on what they need, how far off they typically are, and who reaches for them.

Notice the pattern: accuracy improves as you add information. Parents' heights alone give a genetic ceiling and floor. Add the child's own measurements and you sharpen the guess. Add an X-ray of skeletal maturity and you get the tightest number a clinic can offer without waiting for the child to finish growing. This page blends the first two of those inputs.

How the Predicted Adult Height Calculator Works

The tool combines two independent signals. The first is canalization — the well-documented tendency of healthy children to grow along a fixed percentile channel. A boy at the 60th percentile for height at age 6 is very likely to still be near the 60th percentile at age 18. So the calculator reads your child's current height-for-age percentile and projects that same percentile onto the adult height distribution.

The second signal is the genetic target. When you enter both parents' heights, the calculator computes the Tanner mid-parental height: the average of the two parents, plus 6.5 cm for a boy or minus 6.5 cm for a girl. That 6.5 cm is half the roughly 13 cm average gap between adult men and women. If you want that genetic figure on its own, the dedicated mid-parental height calculator shows the full target band.

The final prediction is a weighted blend of these two. The weighting shifts with age: for a 4-year-old, the genetic target carries almost half the weight because the child's own trajectory is still settling. For a 16-year-old, the child's current height carries about 90% of the weight, because by then most of the growing is done and the percentile channel is locked in. That is why the “likely range” on this page shrinks from about ±9 cm at age 4 to under ±5 cm in the mid-teens.

Worked Example: An 8-Year-Old Boy

Take a boy who is exactly 8 years old and 128 cm tall, with a 180 cm father and a 165 cm mother. Here is each step the calculator runs:

1. Current percentile. At age 8, the median height for boys is about 128 cm, so 128 cm sits right at the 50th percentile (z-score ≈ 0).
2. Trajectory estimate. Projecting the 50th percentile forward lands on the adult male median, roughly 177 cm.
3. Genetic target. (180 + 165) ÷ 2 = 172.5 cm; add 6.5 cm for a boy = 179 cm.
4. Blend. At age 8 the trajectory gets about 59% of the weight and genetics 41%: 0.59 × 177 + 0.41 × 179 ≈ 178 cm.
5. Range. With an ±8 cm band at this age, the likely adult height is roughly 170–186 cm (about 5'7" to 6'1").

Change one input and watch the number move: if that same boy were already 138 cm at age 8 (near the 90th percentile), the trajectory estimate jumps to about 186 cm and pulls the blend up with it. The parents' heights anchor the estimate, but the child's own head start or lag is what moves it most.

The Khamis-Roche Method Explained

The Khamis-Roche method, published in Pediatrics in 1994, is the most accurate way to predict adult heightwithout an X-ray. It uses four inputs — the child's current standing height, weight, exact age, and the mid-parental height — and plugs them into age- and sex-specific regression equations. Roughly 90% of its predictions land within about 2 inches (5 cm) of the child's true adult height, and it is validated for children aged 4 to 17.5 years.

Why does adding weight help? Body mass is a rough proxy for maturity: at the same age and height, a heavier child is often slightly further along in development. The trade-off is that Khamis-Roche relies on published coefficient tables specific to each half-year of age, which is why you usually meet it inside clinical software rather than a one-line formula. The calculator on this page uses the simpler percentile-plus-genetics approach, which needs no coefficient tables and tracks Khamis-Roche closely for children growing along a normal curve.

When a Bone-Age X-ray Wins

Every formula above assumes a child is maturing on a typical schedule. Bone age throws out that assumption and measures maturity directly. A single X-ray of the left hand and wrist is compared against a reference atlas (the Greulich-Pyle method) or scored bone by bone (Tanner-Whitehouse). The Bayley-Pinneau tables then convert the child's current height and bone age into a predicted adult height.

This matters most when chronological age and maturity disagree. A 12-year-old with the bone age of a 9-year-old has far more growing left than the calendar suggests, so a percentile projection would badly undershoot. Pediatric endocrinologists order bone-age films for exactly these cases: suspected growth hormone problems, very early or very late puberty, or a child whose height has crossed two or more percentile lines. If your child's pattern looks unusual on a growth chart, that is a conversation for a doctor, not a calculator.

What Actually Changes Final Height

Prediction error is not random noise; it comes from specific, nameable factors. These are the big ones, with rough magnitudes:

• Puberty timing. Growth plates fuse near the end of puberty — around age 14–15 in girls and 16–17 in boys. An early bloomer shoots up first but stops sooner; a late bloomer often looks short at 13 and then catches up.
• Genetics. Twin studies put the heritability of height near 0.80, meaning most of the variation between people traces to their genes rather than environment.
• Nutrition and chronic illness. Sustained undernutrition, celiac disease, or poorly controlled asthma treated with high-dose steroids can each shave centimeters off the genetic potential.
• The secular trend. Across the 20th century each generation gained roughly 1 cm per decade as nutrition improved — but that rise has largely plateaued in well-fed populations, so today's children rarely overshoot their parents by much.

A child's weight matters here too. Tracking it alongside height on a child growth calculator helps separate a healthy late bloomer from a child whose growth has genuinely stalled.

Reading Your Result Without Over-Reading It

Treat the predicted number as the center of a range, not a promise. A prediction of 178 cm with a ±8 cm band means “most likely somewhere between about 170 and 186 cm.” The single point is the best guess; the width is the honesty. As your child gets older and closer to their final height, that band tightens and the guess gets sharper.

Two patterns are worth a pediatrician's eye rather than a calculator's: a child sitting below the 3rd percentile for their age, or a child whose height crosses percentile channels over time — drifting from the 50th down to the 25th, for example. Steady tracking along any percentile, even a low one, is usually reassuring. It is the change in direction that flags a problem.

Finally, resist the urge to recompute every week. Height moves slowly, and normal measurement error at home is easily 1–2 cm. Measure without shoes, heels against a wall, and check every few months rather than daily. The trend over a year tells you far more than any single day's reading.

References

1. Khamis HJ, Roche AF. “Predicting adult stature without using skeletal age: the Khamis-Roche method.” Pediatrics, 1994.
2. Centers for Disease Control and Prevention. Clinical Growth Charts.
3. Tanner JM, et al. “Prediction of adult height from height, bone age, and occurrence of menarche.” Archives of Disease in Childhood.

Frequently Asked Questions