How tall will my child be? Get an evidence-based estimate of your child's adult height from the parents' heights — the same mid-parental method pediatricians use.
"How tall will my child be?" is one of the first questions parents ask — sometimes before the baby is even born. The most widely used answer comes from the mid-parental height method, described by the growth researcher J.M. Tanner and colleagues in 1970 and still used in pediatric clinics today. The logic is simple: because height is strongly inherited, the average of the parents' heights is the best single starting point for a child's adult height.
The formula averages both parents' heights, then corrects for the average difference between adult men and women — about 13 centimeters (5 inches). For a boy, add 13 cm to the mother's height, add the father's height and divide by two. For a girl, subtract 13 cm from the father's height, add the mother's height and divide by two. This calculator does exactly that, in whichever units you prefer.
The honest caveat is the range. Clinically, a child's target height is quoted as the mid-parental value plus or minus about 8.5 cm (roughly 3.3 inches) — that's the window most children genuinely land in. Siblings share the same mid-parental number yet often end up several centimeters apart, because each child inherits a different mix of height genes and puberty timing.
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| Method | How it works | Best for |
|---|---|---|
| Mid-parental (Tanner) | Averages the parents' heights with a 13 cm sex adjustment. | Any age — even before birth. The classic quick estimate. |
| Khamis-Roche | Combines the child's current age, height and weight with parental height in a research-derived formula. | Children about 4–17 years old; more accurate than mid-parental alone, no X-ray needed. |
| Double at age 2 | Doubles the child's height at age 2 (girls: often 18 months, since they mature faster). | A quick rule of thumb only — fun, but not clinical. |
| Bone age (X-ray) | A hand/wrist X-ray shows skeletal maturity, revealing how much growth remains. | Clinical questions — the most precise method, used by endocrinologists. |
Height is one of the most heritable human traits — studies of twins and families consistently attribute roughly 80 percent of the variation in adult height to genetics, spread across many thousands of gene variants rather than a single "tall gene." That's why parental height predicts so well, and also why it can't predict perfectly: each child draws a unique genetic hand from both parents.
The remaining share belongs to environment, and it matters most while growth is actually happening. Nutrition is the biggest lever — enough total energy, protein, and micronutrients like vitamin D, calcium and zinc. Sleep earns its reputation too: growth hormone is secreted mainly during deep sleep, which is one reason consistent bedtimes genuinely serve growing bodies. Regular physical activity supports healthy bones, and well-managed chronic conditions (asthma, celiac disease, thyroid issues) keep illness from diverting energy away from growth.
Puberty timing shifts the schedule rather than the destination: early developers shoot up sooner but stop sooner, while late bloomers grow longer. Two children with identical predictions can take very different paths to a similar adult height.
A one-time prediction is a snapshot; a growth curve is a movie. Pediatric care tracks height and weight on standardized charts — WHO standards for ages 0–2 and CDC charts from 2 to 20 — and what matters most is that your child follows a reasonably steady percentile line over time, whatever that percentile is. A child cruising along the 25th percentile is growing just as healthily as one on the 75th.
You can see where your child currently lands with our baby growth percentile calculator, which uses the same WHO and CDC data as your pediatrician's charts. Interestingly, a child's percentile in the toddler years tends to correlate with their adult height percentile — another reason steady tracking beats any single formula.
Most height questions are curiosity, not concern — but a few patterns deserve a professional look. Bring it up with your pediatrician if your child crosses two or more major percentile lines on the growth chart (in either direction), grows less than about 4–5 cm per year between age 4 and puberty, is dramatically shorter or taller than the prediction from both parents' heights would suggest, or shows signs of very early or very late puberty.
These situations don't automatically mean something is wrong — children have individual rhythms — but they're exactly what growth monitoring exists to catch. A pediatrician can review the curve, check overall health, and refer to a pediatric endocrinologist for a bone-age assessment if needed. This calculator is a friendly estimate, not medical advice; your child's care team has the full picture.
A mid-parental height prediction is a genuinely useful estimate, but it comes with a wide window: most children end up within about 8.5 cm (roughly 3.3 inches) above or below the predicted number. Genetics account for the majority of adult height, but nutrition, sleep, overall health and the timing of puberty all nudge the outcome. Treat the result as the center of a range, not a promise.
The mid-parental (Tanner) method averages the parents' heights and then adjusts for the average difference between adult men and women, which is about 13 cm (5 inches). For a boy, you add 13 cm to the mother's height, add the father's height, and divide by two. For a girl, you subtract 13 cm from the father's height, add the mother's height, and divide by two.
Doubling height at age 2 is a well-known rule of thumb, and it lands surprisingly close for many children — but it is still a rough shortcut, not a clinical method. Girls mature faster, so a common variant doubles a girl's height at 18 months instead. A pediatrician tracking your child's growth curve over time will always give a better answer than any one-off formula.
The Khamis-Roche method is a research-based prediction formula that uses a child's current age, height and weight together with the parents' heights. Because it incorporates how the child is actually growing, it is generally more accurate than mid-parental height alone for children between about 4 and 17 years old — without requiring an X-ray. The most precise clinical method, bone-age assessment, reads skeletal maturity from a hand X-ray.
You can't change the genetic blueprint, which drives roughly 80 percent of height, but you can help your child reach their full genetic potential. Balanced nutrition with adequate protein, consistent sleep (growth hormone is released mainly during deep sleep), regular physical activity and prompt treatment of chronic illnesses all support healthy growth. No supplement or exercise makes a child grow taller than their genes allow.