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About this tool
Predict a child's adult height from the parents' heights (mid-parental method).
The mid-parental height method estimates how tall a child will end up as an adult by averaging both parents' heights after adjusting for the child's sex: for a boy, (mother + father + 13) / 2 in centimetres, and for a girl, (mother + father - 13) / 2. This calculator applies that formula and reports the result with its usual confidence band of about plus or minus 8.5 cm, plus a feet-and-inches conversion. It is an informational estimate of genetic potential, not a diagnosis or a measurement of your child.
Open Child Height Predictor on AltFTool — it loads instantly in your browser.
Type both measurements into the Mother's height (cm) and Father's height (cm) number fields, which open prefilled with 165 and 178 — centimetres are the only unit the tool accepts
Pick from the Child's sex dropdown, whose two options are Boy and Girl: Boy adds 13 cm to the parents' combined height before halving it, Girl subtracts 13 cm
The prediction appears as you type, with no button to press — a height in cm under the caption predicted adult height, alongside a Likely range card (that figure ±8.5 cm) and an In feet card, with a footnote that this is a statistical estimate and actual height depends on nutrition, health and genetics
The same mid-parental calculation used in growth assessment, with the 13 cm sex adjustment applied in the correct direction for boys and girls.
A likely band of roughly 17 cm total width is reported alongside the point estimate, because the method is genuinely that imprecise.
Centimetres and feet-and-inches are shown together, so you can use whichever your growth chart or family uses.
Add both parents' heights in centimetres, add 13 cm for a boy or subtract 13 cm for a girl, then divide by two. So a 165 cm mother and a 178 cm father give roughly 178 cm for a son and 165 cm for a daughter.
It is a population estimate with a wide margin: about plus or minus 8.5 cm, meaning roughly a 17 cm spread within which most children in that family land. Two siblings with the same parents can differ substantially and both be entirely normal.
Because 13 cm is approximately the average adult height difference between men and women, so the adjustment shifts the parental average onto the child's own sex-specific scale. It is a correction for that population gap, not a claim about any individual child.
Yes. The formula reflects genetic potential only; nutrition, sleep, chronic illness, hormone conditions and timing of puberty all affect the height actually reached. If a child is growing much slower or faster than expected, or crossing centile lines on a growth chart, that is a question for a paediatrician rather than a calculator.