Child Height Predictor - Khamis-Roche Method
One of the more accurate height prediction methods that does not require the measurement of bone age. Uses the child's current height, weight, and the average of both parents' heights. Most accurate for children ages 4–9.
Child Height Predictor - Based on Parents' Heights Only
This method estimates a child's adult height based only on the parents' heights using the mid-parental height formula. It does not require the child's current measurements.
Convert between US and metric height units.
A height calculator predicts a child's adult height using established medical methods and compares current height to age- and sex-matched population norms. This page offers two prediction calculators and a height unit converter:
Both predictors display results alongside a CDC Stature-for-Age percentile growth chart, placing the predicted adult height against the standard population distribution for boys or girls ages 2–20.
"How tall will I be?" or "how tall will my child be?" are questions that are often asked. Height is largely (60–80%) determined by genetics, though environmental factors also play an important role. The environment that a person is raised in affects their height, particularly during the growing years. Factors such as nutrition, health conditions, and physical activity can significantly influence final adult stature.
Children's heights tend to regress toward the mean. Very tall or short parents are likely to have a taller or shorter child than average, but the child is likely to be closer to the average height than their parents. For example, a father who is 7 ft tall is likely to have a child who is shorter than him, while a mother who is 4 ft 11 in is likely to have a child who is taller than her. This is because extremes in height are often not maintained from generation to generation.
Growth patterns also differ by sex. Girls typically stop growing at age 14–16, while boys generally continue growing until age 16–18. Growth plateaus occur after the growth plates (epiphyseal plates) in the long bones close, which corresponds roughly to the end of puberty.
The simplest and most widely used approach requires only the parents' heights. Developed by pediatric endocrinologist James Tanner, the formula adjusts for the average height difference between adult men and women (approximately 5 inches / 13 cm):
Worked example: Father is 5 ft 11 in (71 in), mother is 5 ft 5 in (65 in).
The typical prediction range is ±2 inches (±5 cm), meaning most children fall within this window of their mid-parental target. This range reflects genetic variation - the many genes involved in height don't always combine in the mathematically expected way.
One of the more accurate height prediction methods that does not require the measurement of bone age. Developed by Harry Khamis and Alex Roche in 1994, this method uses the child's current height, weight, and the average of the two parents' heights (mid-parent stature) to predict adult height.
The method works by combining two signals:
These two signals are blended using an age-dependent weighting: for younger children (age 4–5), the mid-parental height carries more weight because the child's current growth trajectory is less predictive. For older children (age 8–9), the child's own growth trajectory becomes more informative and carries more weight.
The prediction comes with a standard error of approximately 2.1 inches (5.3 cm) for boys and 1.7 inches (4.3 cm) for girls. This means approximately 68% of children will reach an adult height within ±1 standard error of the prediction - a range of about 4–5 inches total. The method is most accurate for children ages 4–9 and was developed primarily on Caucasian children, so results may vary for other populations.
This method involves taking an X-ray of the child's left hand and wrist to determine skeletal maturity - referred to as bone age. The Greulich-Pyle method uses a standardized atlas of bone development (based on data from 1931–1942) to estimate how much growth remains. The Roche-Wainer-Thissen (RWT) method is one of the most statistically valid approaches. Because bone age can differ from chronological age - an 8-year-old can have the skeletal maturity of a 6-year-old or a 10-year-old - this method is particularly useful for children with delayed or advanced puberty. These methods require medical equipment and a trained clinician to interpret the X-rays, so they are not replicated in this calculator.
A very rough rule of thumb: a boy's height at age 2 years, doubled, gives an approximate adult height estimate. For girls, double the height at 18 months. For example, a boy measuring 35 inches at age 2 would be predicted to reach approximately 70 inches (5 ft 10 in) as an adult. This method has a large margin of error and is best used only as a casual estimate when other information is unavailable.
The reason height prediction matters most during childhood is that all height increases occur at the growth plates - specialized cartilage zones near the ends of long bones (femur, tibia, humerus, etc.) called the epiphyseal plates. These plates contain actively dividing cells that push the bone outward, making it longer.
When puberty concludes, rising levels of sex hormones (estrogen in girls, testosterone in boys) cause the growth plates to harden and fuse - a process called epiphyseal fusion. Once fused, no further lengthening of the bone can occur and adult height is fixed. Growth plate fusion typically completes:
This is why bone age can be so informative: a child with delayed bone age (growth plates younger than chronological age) has more remaining growth potential than a child with an advanced bone age, even if both are the same height and calendar age.
The following table shows median (50th percentile) heights by age for U.S. children based on CDC growth chart data:
| Age | Boys (50th pct) | Girls (50th pct) |
|---|---|---|
| 2 years | 2 ft 11 in (87.8 cm) | 2 ft 10 in (86.0 cm) |
| 4 years | 3 ft 4 in (102.2 cm) | 3 ft 3.5 in (100.3 cm) |
| 6 years | 3 ft 9.5 in (114.4 cm) | 3 ft 8.5 in (112.8 cm) |
| 8 years | 4 ft 2 in (125.9 cm) | 4 ft 1 in (124.0 cm) |
| 10 years | 4 ft 6 in (136.5 cm) | 4 ft 5 in (134.6 cm) |
| 12 years | 4 ft 11 in (149.1 cm) | 5 ft 0.5 in (153.7 cm)* |
| 14 years | 5 ft 4.5 in (163.8 cm) | 5 ft 3.5 in (161.2 cm) |
| 16 years | 5 ft 8.5 in (173.9 cm) | 5 ft 4 in (163.0 cm) |
| 18 years | 5 ft 9.5 in (176.8 cm) | 5 ft 4.5 in (163.7 cm) |
| 20 years | 5 ft 10 in (178.0 cm) | 5 ft 5 in (165.5 cm) |
*Girls typically experience their growth spurt earlier than boys, which is why the median 12-year-old girl is slightly taller than the median 12-year-old boy.
Average adult height varies substantially around the world, driven by genetics, nutrition quality, healthcare access, and historical socioeconomic conditions. Countries with consistently high standards of living and nutrition tend to have the tallest populations:
| Country | Average Male Height | Average Female Height |
|---|---|---|
| Netherlands | 6 ft 0 in (182.9 cm) | 5 ft 6.5 in (170.4 cm) |
| Denmark | 5 ft 11.5 in (181.9 cm) | 5 ft 6.5 in (169.5 cm) |
| Germany | 5 ft 11 in (180.3 cm) | 5 ft 5.5 in (166.3 cm) |
| Australia | 5 ft 11 in (179.2 cm) | 5 ft 5 in (165.8 cm) |
| United States | 5 ft 9.5 in (176.8 cm) | 5 ft 4 in (162.5 cm) |
| United Kingdom | 5 ft 9.5 in (175.3 cm) | 5 ft 4.5 in (161.9 cm) |
| China | 5 ft 7 in (171.8 cm) | 5 ft 2.5 in (159.7 cm) |
| Brazil | 5 ft 8.5 in (173.5 cm) | 5 ft 3 in (161.3 cm) |
| India | 5 ft 5 in (165.3 cm) | 5 ft 0.5 in (152.6 cm) |
| Philippines | 5 ft 4.5 in (163.7 cm) | 5 ft 0 in (151.8 cm) |
Average heights have increased dramatically in most countries over the past century - a phenomenon called the secular trend - primarily due to improvements in childhood nutrition and reduction of infectious disease. The Netherlands gained approximately 8 inches in average male height between 1860 and 2000.
Height, for better or for worse, is largely (60–80%) determined by genetics. Barring any medical conditions, there is not much that can be done to increase height significantly once a person has reached adulthood - the growth plates in the bones have closed. However, during the growing years, optimizing the following factors can help a child reach their genetic height potential:
Recombinant human growth hormone (rhGH) therapy is FDA-approved for several conditions that affect growth in children, including:
When started early enough (well before growth plate fusion), rhGH therapy can add 1–3 inches to final adult height for children with GHD, and somewhat less for other indications. Treatment requires daily injections, typically for several years, and is medically supervised by a pediatric endocrinologist. It is not appropriate for children of normal stature who simply want to be taller.
Human growth follows a predictable pattern, though the timing varies by individual:
A height percentile tells you what percentage of children of the same age and sex are shorter than the measured child. For example:
Any percentile between the 3rd and 97th is generally considered within the normal range. What matters most clinically is that the child maintains a consistent percentile over time - a child who has always been at the 15th percentile is growing normally, while a child who drops from the 60th percentile to the 20th percentile over two years warrants evaluation. A sudden drop of more than 20–25 percentile points warrants a pediatric evaluation regardless of absolute percentile.
No height prediction method is perfectly accurate. The Khamis-Roche method - the most accurate non-bone-age method - has a standard error of about 2.1 inches for boys and 1.7 inches for girls. This means about 68% of children will fall within that range of the prediction, and about 95% will fall within twice that range (roughly ±4 inches). Height is influenced by too many genetic and environmental variables for any formula to predict it exactly. Think of the result as the center of a probability distribution, not a guaranteed outcome.
Most boys stop growing in height between ages 17 and 20, though the majority of height gain is complete by 16–17. The final 1–2 inches often come slowly over the last year or two of growth. Boys who go through puberty later (late bloomers) may continue growing until 20 or even 21. The definitive signal that growth has stopped is fusion of the epiphyseal growth plates, which can be confirmed with a hand and wrist X-ray showing bone age of 18–19 years or higher.
Most girls stop growing in height between ages 14 and 16, typically 2–3 years after their first menstrual period (menarche). Girls who start puberty earlier tend to stop growing earlier. After menarche, most girls grow only 1–3 more inches before their growth plates fuse. Reaching 5 feet is typically complete well before the end of high school for most girls.
No. Once the growth plates have fused, no exercise can increase skeletal height. Hanging, yoga, and spinal decompression exercises can temporarily decompress spinal discs and improve posture, which may allow you to stand up to half an inch taller than your slouched baseline - but this is not a true increase in bone length. Good posture is still worthwhile for appearance, health, and avoiding back pain.
It works in the sense that the formula correctly estimates what height the child would reach based on the biological parents' genetics. For an adopted child whose biological parents' heights are unknown, the mid-parental formula cannot be used. Instead, the Khamis-Roche method (using the child's own current growth trajectory plotted on a CDC growth chart) may offer a better estimate, since a child's current height percentile is itself a reflection of their genetic potential plus environmental factors to date.
Not necessarily. A child below the 3rd percentile, or one who is crossing percentile lines downward, warrants medical evaluation. But a child who has consistently tracked at the 5th percentile since infancy - especially one with parents who are also shorter than average - is likely following their own normal growth curve. Pediatricians evaluate height in the context of growth velocity (the rate of change over time), parental heights (mid-parental target), and bone age, not just a single percentile measurement.
Constitutional delay of growth and puberty (CDGP) is the most common cause of late puberty and a delayed growth spurt. It is a normal variant - not a disease - and tends to run in families. Children with CDGP grow at a normal rate but enter puberty later than average, so they appear shorter than peers in early adolescence. They ultimately reach a normal adult height once their growth spurt occurs, often in the later teen years. A pediatric endocrinologist can distinguish CDGP from true growth hormone deficiency or other treatable causes of short stature using bone age X-ray and growth velocity tracking.