Adolescent Final Height Prediction Calculator

The MPH method predicts adult height within ±8.5 cm (1 standard deviation) for about 68% of children, and within ±17 cm for about 95%. A bone-age X-ray analyzed with the Greulich-Pyle atlas narrows the error to ±2–3 cm, making it far more precise for clinical decisions. The NIH and American Academy of Pediatrics both recommend bone-age assessment when the height prediction is more than 2 SD from the MPH target.

On average, girls reach final adult height between ages 15–17, since the growth plates (epiphyses) fuse roughly 2 years after menarche. Boys typically stop growing between ages 17–19, though some continue adding millimeters until age 21. According to CDC growth charts, height velocity in boys peaks around age 13.5 (≈9 cm/year) and in girls around age 11.5 (≈8 cm/year).

The 13 cm (sometimes cited as 12.7 cm or 5 inches) represents the average height difference between adult males and females globally, derived from WHO and NCHS reference populations. Adding it adjusts the mother's height to a 'male equivalent' for boys; subtracting it adjusts the father's height to a 'female equivalent' for girls, so both sexes are compared on the same scale before averaging.

Yes, but the effect is most significant during early childhood. USDA and WHO data indicate that severe, prolonged malnutrition during the first 1,000 days of life can reduce adult stature by 5–10 cm. During adolescence, adequate protein (0.85 g/kg/day per USDA Dietary Guidelines 2020–2025), calcium (1,300 mg/day for ages 9–18 per NIH), and vitamin D remain important for achieving genetic potential, but supplementing beyond needs provides no additional height benefit.

No. Growth hormone deficiency (GHD), Turner syndrome, skeletal dysplasias, and other medical conditions cause growth patterns that fall outside the normal distributions these formulas assume. The NIH National Institute of Child Health and Human Development states that children with GHD can grow as little as 4 cm/year (vs. a normal 5–6 cm/year baseline). These children require serial bone-age assessments and endocrinologist-supervised height prediction, not formula-based estimates.

A gap of more than 2 standard deviations (>17 cm) between the predicted height and the MPH target warrants pediatric evaluation. Possible causes include hypothyroidism, celiac disease, GHD, or chronic illness. The CDC and AAP recommend plotting height velocity on a growth chart: a velocity below the 25th percentile for age and sex over 6–12 months is a clinical red flag regardless of the absolute height.

Early puberty triggers faster growth but earlier growth-plate fusion, often resulting in a shorter adult height despite a tall childhood stature. NIH defines precocious puberty as onset before age 8 in girls and age 9 in boys. Late puberty delays the growth spurt; boys with constitutional delay may not peak until ages 15–16 but often reach a normal MPH target. This calculator uses chronological age, so children with significantly early or late puberty should interpret results cautiously and consult a pediatric endocrinologist.

Without parental heights, only the Bayley-Pinneau age/sex percentage method can be used. The estimate is still useful — for a 13-year-old boy at 160 cm, it yields ~183 cm — but the likely range widens to ±12–15 cm because the genetic component is unknown. For adopted children with significant ethnic background differences from the population norms, clinicians sometimes substitute ethnic-specific growth references (e.g., WHO Multicentre Growth Reference vs. CDC 2000 charts) for better accuracy.