What it is
Mid-parental height (MPH), or target height, estimates the genetic potential for a child’s adult stature from the heights of their two biological parents. It is a quick anchor used during growth assessment: a child tracking far from their target prompts a closer look. It estimates potential — it is not a prediction of the exact adult height.
The method
The Tanner formula corrects for the average adult height difference between the sexes (~13 cm), then averages the parents:
- Boys: (father’s height + mother’s height + 13) ÷ 2
- Girls: (father’s height + mother’s height − 13) ÷ 2
All heights in centimetres. Around the resulting target, a band of ±8.5 cm is applied — this approximates the mid-parental ±2 SD range and covers roughly the 3rd–97th centile of expected adult outcomes for that child.
When to use it
Use it in any short-stature or tall-stature workup, and whenever a child’s height-for-age centile seems discordant with the family. The clinical question is not “what is the number?” but “is the child’s current growth trajectory consistent with their target?” Plot the child’s projected adult height (or current centile) against the target band:
- Tracking within the band → reassuring, consistent with genetic potential.
- Falling well below the band → investigate (constitutional delay, endocrine, chronic disease, nutrition).
- Well above the band → consider tall-stature causes if growth is accelerating.
Worked example
A girl with father 178 cm and mother 165 cm:
target = (178 + 165 − 13) ÷ 2 = 330 ÷ 2 = 165 cm
Target range = 165 ± 8.5 = 156.5–173.5 cm. If her projected adult height from current centiles lands in this band, her growth is consistent with her genetic potential. A boy with the same parents would be (178 + 165 + 13) ÷ 2 = 178 cm, range 169.5–186.5 cm.
Pitfalls and caveats
- It is an estimate of potential, not a prediction. Marked deviation of measured/projected height from the target band warrants assessment, not reassurance.
- Garbage in, garbage out — reported parental heights are often inaccurate; measure parents in clinic where it matters.
- Ignores the child’s own data — it does not use the child’s current height, weight, bone age or pubertal stage. Bone-age-based methods (e.g. Bayley-Pinneau, Khamis-Roche) individualise the estimate.
- Assumes both biological parents reached their own genetic potential — parental stunting from childhood illness or undernutrition biases the target downward.
Run it: Mid-Parental Target Height
Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.