How this is calculated
The mid-parental target height method, described by Tanner and colleagues, averages the two parents' heights and then adjusts for sex — because adult men average about 5 inches (13 cm) taller than adult women.
- For a boy: (mother's height + father's height + 5 in) ÷ 2
- For a girl: (mother's height + father's height − 5 in) ÷ 2
Then comes the part most online calculators skip: the range. Genetics is a spectrum, not a coordinate. Real adult height usually falls within about 2 to 4 inches (5 to 10 cm) either side of the mid-parental figure. A calculator that gives you a single confident number is overselling what two parental measurements can tell it.
A more accurate method — and why it isn't here
For children aged 4 to 17, the Khamis-Roche method is the most accurate approach that doesn't involve an X-ray. It improves on the parental average by adding the child's current height, current weight and age, weighted by age- and sex-specific coefficients derived from the Fels Longitudinal Study. Its margins of error are roughly ±2.1 inches for boys and ±1.7 inches for girls — meaningfully tighter than the mid-parental method.
I have deliberately not implemented it here, because doing so requires the published coefficient tables, and I would rather give you an honest simpler estimate than a more impressive-looking one built on numbers I guessed at. If you want a Khamis-Roche prediction, ask your paediatrician — they have access to it.
The clinical gold standard: bone age
When a doctor needs a genuinely accurate estimate — usually to investigate delayed or precocious puberty — formulas are set aside in favour of a hand and wrist X-ray, read against the Greulich-Pyle atlas.
What this reveals is the state of the growth plates, the cartilage zones near the ends of the long bones where new bone is laid down. A radiologist compares their maturation against standard images to establish skeletal age, which can run ahead of or behind chronological age. As sex hormones peak towards the end of puberty, those plates fuse into solid bone — and once fused, linear growth stops permanently. Knowing how much growth plate remains is far more informative than any formula.
What actually influences whether you reach your potential
Puberty timing
This is the biggest source of variation, and the most misunderstood. Children who enter puberty early hit their growth spurt sooner and shoot ahead of classmates — but their growth plates also fuse earlier, cutting the total time available to grow.
Children with constitutional delay — the classic "late bloomers" — spend years being the shortest in their year group, then keep growing steadily after their peers have stopped. They frequently catch up entirely, and sometimes overtake their earlier predicted percentile. If you are 14 and shorter than everyone, that is genuinely not the end of the story.
Sleep
The pituitary gland releases the great majority of human growth hormone in pulses during stage N3 slow-wave sleep — the deepest part of the night. Chronic sleep deprivation or fragmented sleep suppresses that nocturnal release, and it does so precisely during the years when it matters most. Of everything on this page you can actually control, sleep is the one with the clearest mechanism.
Nutrition
Bone elongation is expensive. Sustained calorie restriction — from severe dieting, from intense athletic training without matching intake, or from an eating disorder — makes the body divert energy away from growth. Adequate protein matters, and so do vitamin D, calcium and zinc, which are required co-factors for bone mineralisation and cell division; zinc deficiency in particular blunts growth directly.
This is worth stating plainly to any teenager reading: undereating during your growing years can cost you height you don't get back. If food and body image are difficult for you right now, that is worth telling someone about — a parent, a doctor, or a school nurse.
Medical conditions and medications
Conditions causing malabsorption — undiagnosed coeliac disease, inflammatory bowel disease — can stunt growth, sometimes with poor growth as the first visible sign. So can endocrine problems such as hypothyroidism or growth hormone deficiency. Long-term high-dose oral corticosteroids, prescribed for severe asthma or autoimmune disease, suppress growth velocity as a known side effect.
All of these are things a doctor can identify and, in many cases, treat.
When to actually see a doctor
Rather than watching a calculator, see your doctor if any of these apply:
- Growth has clearly slowed or stopped compared with previous years
- A child is much shorter or taller than expected for the family
- Puberty has started very early (before 8 in girls, 9 in boys) or has not begun by 13 in girls or 14 in boys
- Growth is accompanied by fatigue, persistent digestive symptoms, or unexplained weight loss
A doctor plotting height over time on a growth chart learns more from two measurements a year apart than any formula can tell you from a single day.
One last thing, for the teenagers
Height gets a great deal of attention during adolescence and very little afterwards. It is almost entirely outside your control, it is a poor predictor of health, happiness or anything else that matters, and the timing differences that feel enormous at 14 have usually evened out by 20. Sleep well, eat properly, and let your growth plates do their work.
References
- Tanner JM, Goldstein H, Whitehouse RH. Standards for children's height at ages 2–9 years allowing for heights of parents. Arch Dis Child. 1970;45(244):755–762. doi:10.1136/adc.45.244.755 The mid-parental target height method used by this calculator.
- Khamis HJ, Roche AF. Predicting adult stature without using skeletal age: the Khamis-Roche method. Pediatrics. 1994;94(4 Pt 1):504–507. The more accurate method described above, which adds current height, weight and age. Not implemented here.
- Greulich WW, Pyle SI. Radiographic Atlas of Skeletal Development of the Hand and Wrist. 2nd ed. Stanford, CA: Stanford University Press; 1959. The atlas against which bone age is assessed.
- Takahashi Y, Kipnis DM, Daughaday WH. Growth hormone secretion during sleep. J Clin Invest. 1968;47(9):2079–2090. doi:10.1172/JCI105893 Established that growth hormone is released mainly during deep slow-wave sleep.
- Marshall WA, Tanner JM. Variations in pattern of pubertal changes in girls. Arch Dis Child. 1969;44(235):291–303. · Variations in the pattern of pubertal changes in boys. Arch Dis Child. 1970;45(239):13–23. The staging work underlying the discussion of early and late puberty.