Child height predictor,
powered by genetics.

Science behind the prediction

How to predict a child's adult height.

Adult height is one of the most heritable human traits. Twin studies consistently find that 60–80% of height variation is explained by genetics, with the remainder due to nutrition, sleep quality, and overall health during childhood. The simplest practical way to use this genetic signal is the Mid-Parental Height (MPH) method, first published by Tanner, Goldstein, and Whitehouse in 1970.

The Mid-Parental Height formula

The formula takes both parents' heights (in centimetres) and applies a gender-specific offset to account for the average height difference between men and women (~13 cm):

The result is the genetic mid-point for a child of those parents. It does not guarantee that height. It is the centre of a statistical distribution. One standard deviation spans ±8.5 cm (±3.4 in), meaning roughly two-thirds of children of parents with the same mid-parental height will fall inside that band.

Worked example

Father: 182 cm. Mother: 168 cm. Child: boy.

• MPH = (182 + 168 + 13) ÷ 2 = 363 ÷ 2 = 181.5 cm
• 68% range: 173 – 190 cm (±8.5 cm)
• 95% range: 164.5 – 198.5 cm (±17 cm)

In imperial: father 5'11.7", mother 5'6.1", predicted son: 5'11.5" (175–190 cm likely range).

Why genetics does not fully determine height

The MPH formula captures the genetic component, but final adult height also depends on:

• Nutrition: protein, calcium, and micronutrient intake during puberty are the biggest environmental levers. Chronic undernutrition can cost several centimetres.
• Sleep: ~80% of growth hormone is secreted during deep sleep. Consistent adequate sleep is especially important between ages 9–16.
• Illness and stress: prolonged illness or glucocorticoid use can slow growth velocity temporarily. Most children show a "catch-up" period when the illness resolves.
• Timing of puberty: early puberty causes a temporary acceleration, followed by an earlier stop. Late puberty reverses this pattern. Both pathways typically end at similar adult heights for the same genetic background.

Limitations of the formula

The MPH method is a population-level statistical model, not an individual certainty. Key limitations:

• It assumes both parents represent typical phenotypic expression of their genotype. A parent who grew up malnourished will pass on taller genes than their own height suggests.
• The formula was derived from European populations. Ethnic background affects mean height, so the ±8.5 cm SD is an approximation.
• It does not account for any known height-related medical conditions (growth hormone deficiency, Turner syndrome, etc.).

When to consult a paediatrician

If a child's current height is tracking more than two standard deviations below the mid-parental prediction or if their growth velocity drops sharply. This is worth discussing with a paediatrician. A growth chart centile analysis and bone age X-ray can reveal whether the trajectory is simply a late-bloomer pattern or requires investigation.

Disclaimer

This calculator is for informational purposes only and should not replace professional medical advice. Height predictions are estimates with substantial uncertainty. If you have concerns about your child's growth, consult a paediatric endocrinologist.