Height Calculator
Estimate how tall a child will grow using the mid-parental method: average the parents' heights and adjust by 2.5 inches for a boy or a girl. The steps and the expected ±4-inch range are shown — genetics sets a range, not a point.
Mid-parental height formula
The mid-parental (Tanner) method is the classic pediatric estimate: average the mother's and father's heights, then add 2.5 in (6.5 cm) for a boy or subtract 2.5 in for a girl. Most children end up within about ±4 inches (±10 cm) of the estimate.
More precise methods exist — the Khamis-Roche formula adds the child's current age, height and weight, and bone-age X-rays are the clinical gold standard. Mid-parental is the one you can compute from parents' heights alone, and it's what pediatricians sketch as the "target height" on growth charts.
Worked examples
Example 1: son of 5′4″ and 5′10″ parents
Mother 5′4″, father 5′10″ — predicted height for a boy?
- Convert to inches and average.(64 + 70) ÷ 2 = 67 in
- Add 2.5 inches for a boy.67 + 2.5 = 69.5 in
About 5′9½″ (177 cm), most likely between 5′5½″ and 6′1½″.
Example 2: daughter of the same parents
Same parents — predicted height for a girl?
- Same mid-parental average.67 in
- Subtract 2.5 inches for a girl.67 − 2.5 = 64.5 in
About 5′4½″ (164 cm) — close to her mother's height.
Example 3: doubling the two-year-old's height
Folk rule: adult height ≈ 2 × height at age 2. A 34-inch two-year-old boy?
- Double the age-2 height.34 × 2 = 68 in
- Compare with mid-parental for the same family — both are rough estimates.68 vs 69.5 in
Both rules land near 5′8″–5′10″; agreement between methods raises confidence.
FAQ
How accurate is the mid-parental method?+
It predicts the genetic target, and about 95% of children land within ±4 inches (±10 cm). Nutrition, health and puberty timing explain why siblings with the same target differ.
At what age can you predict adult height best?+
The older the child, the better: by the teen growth spurt, current height percentile tracks adult height closely. Clinically, a bone-age X-ray read with the Greulich-Pyle atlas gives the tightest prediction.
Do boys really grow until 18 and girls until 16?+
Roughly: girls typically finish within ~2 years after their growth spurt peak (around 14–16), boys later (16–18), with individual variation. Growth plates closing, not a birthday, is the real endpoint.
Does the formula work in centimeters?+
Yes — average the parents in cm and add/subtract 6.5 cm. This page shows the result in both inch and cm form.
My child is far below the predicted range — should I worry?+
Percentile crossing (dropping channels on the growth chart) matters more than any formula. That's a question for a pediatrician, who will look at growth velocity, not a one-time number.
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