"I'm short, my partner is short — can our child still end up at a normal height?" The answer: yes, it's possible, but the odds are low. Genetics accounts for about 80% of height variance, but the remaining 20% — environment plus the regression-to-mean phenomenon — leaves room for "escape."
How heritable is height?
The heritability coefficient is h² = 0.75-0.85, particularly in developed populations where nutrition and disease are non-limiting. This means 75-85% of height variance is genetic, with 15-25% from other factors.
Mid-Parental Height (MPH): Tanner formula
The simplest, most widely used adult-height estimate:
- Boys: MPH = (father_cm + mother_cm + 13) ÷ 2
- Girls: MPH = (father_cm + mother_cm − 13) ÷ 2
"+13" / "−13" represents the average sex difference in adult height.
Expected range: MPH ± 8.5 cm — about 95% of children land in that window.
Example
Father 168 cm, mother 158 cm:
- Boy: MPH = (168 + 158 + 13) / 2 = 169.5 cm. Expected: 161-178 cm.
- Girl: MPH = (168 + 158 − 13) / 2 = 156.5 cm. Expected: 148-165 cm.
Regression to the mean — children usually differ from parents
Galton (1886): children of very tall parents tend to be slightly shorter; children of very short parents tend to be slightly taller. This statistical phenomenon is called regression to the mean.
| Avg of parents | Expected boy's height |
|---|---|
| 150 cm | ~163 cm (regress up) |
| 160 cm | ~168 cm |
| 170 cm | ~173 cm |
| 180 cm | ~177 cm (regress down) |
| 190 cm | ~181 cm |
So a child from a short family is statistically expected to be 5-10 cm taller than the parents — though not always.
When the 20% "environmental" share matters
To reach the genetic ceiling:
- Nutrition — adequate protein, iron, zinc, vitamin D, calcium
- Sleep quality — GH peaks at sleep onset
- Regular exercise — but excessive loading can damage epiphyses
- Absence/management of chronic disease — celiac, IBD, CKD, thyroid disorders
- Low chronic stress — psychosocial short stature is a real diagnosis
- Endocrine integrity — GH, IGF-1, thyroid, sex hormones
Historical: 20th-century European mean adult height rose by +10 cm. Genes didn't change — environment did. Most of this "secular trend" is nutrition plus sanitation.
Asymmetric parental heights
Mother 180, father 165 — the MPH formula gives the midpoint. But because height is polygenic, sons may correlate slightly more with fathers (r ≈ 0.45) and daughters with mothers (r ≈ 0.50). Both inputs are important — single-parent prediction is not reliable.
"Sign them up for swimming, they'll grow" — myth
False. Swimming, basketball, volleyball don't make children taller — selection bias does. Children already tall get selected. Exercise that doesn't damage growth plates is the realistic goal.
FAQ
My father is 165, mother 155, and my son is 175 at age 18 — how?
Regression to the mean + good nutrition + good health + likely tall genes from grandparents. Because height is polygenic, generational "jumps" are possible.
When are growth-hormone-stimulating medications prescribed?
Only for documented indications: GH deficiency, Turner syndrome, Prader-Willi, chronic kidney disease, idiopathic short stature (height <p1) — under pediatric endocrinology supervision. Misuse causes serious side effects (acromegaly, edema, cancer risk).
Can MPH be wrong?
About 5% of children fall outside the MPH ± 8.5 cm window. For more precise prediction (especially with bone age data), use Bayley-Pinneau or Khamis-Roche.
Bottom line
Parental height is the strongest single predictor of a child's adult height, but it's not the only factor. Regression to the mean + good environment + good health means your child can end up 5-10 cm different from family expectation.
Our free MPH calculator gives you the expected range in seconds. For greater precision (bone age + current measurements), upgrade to Premium and try Khamis-Roche or Bayley-Pinneau.