Mid-parental height: the target your genes suggest

The formula

Let father's height be F and mother's height be M (same units):

• Boys: target = (F + M + 13) ÷ 2
• Girls: target = (F + M − 13) ÷ 2

The ±13 cm sex adjustment reflects average adult height differences between men and women. The 13 cm is added before dividing, which is equivalent to shifting the midpoint by 6.5 cm.

Worked example: father 178 cm, mother 165 cm. Boy's target: (178 + 165 + 13) ÷ 2 = 178 cm. Girl's target: (178 + 165 − 13) ÷ 2 = 165 cm.

Why the corridor matters more than the number

Height is polygenic — influenced by many genes from both sides of the family — so the mid-parental target is a center point, not a destiny. In pediatric use, the target is quoted with a corridor (commonly ±7.5 to ±10 cm; GrowTall displays ±8.5 cm) within which the large majority of children land.

A child tracking steadily anywhere inside the corridor is doing exactly what their genes suggest. That makes the corridor a wonderfully calming tool: it reframes "why aren't they taller?" into "are they tracking their own path?"

When distance from target is worth a conversation

Pediatricians use the mid-parental target as context: a child whose height tracks far below — or far above — the family corridor, especially alongside slowing growth velocity, is a candidate for a routine pediatric evaluation. This is screening context, not diagnosis.

Mid-parental height in GrowTall

Enter both biological parents' heights once, and GrowTall draws the target range on a visual scale beside your child's trajectory, updating as they grow (GrowTall Plus). Pair it with the Khamis-Roche estimate for the fullest picture.