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Mid-Parental Height Calculator

Enter both parents' heights and the child's sex to predict adult height.

How it is calculated

Heights are entered in centimetres. For a boy the tool uses H = (father + mother + 13) ÷ 2, and for a girl H = (father + mother − 13) ÷ 2. The 13 cm is the assumed average height gap between men and women, which is why half of it (6.5 cm) is added or subtracted after averaging. The expected range is H − 8.5 to H + 8.5 cm. The prediction is also converted to feet and inches (H ÷ 2.54 gives inches). Both parent heights must be above zero. Any sex value other than girl is treated as boy. The tool does not check whether a height is realistic and does not use the child's current height or growth pattern.

Worked example

Father 180 cm, mother 165 cm, and the child is a girl. Sum: 180 + 165 = 345. Subtract 13: 345 − 13 = 332. Halve: 332 ÷ 2 = 166.0 cm. Range: 166 − 8.5 = 157.5 to 166 + 8.5 = 174.5 cm. In inches: 166 ÷ 2.54 = 65.35, which is 5 ft 5.4 in. For a boy with the same parents the result would be 179.0 cm.

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Common mistakes

  • Entering parent heights in inches or feet. The tool expects centimetres, so 70 for a 70 inch father would give a result far below any real height.
  • Choosing the wrong sex. The two settings differ by 13 cm for the same parents, which is larger than the 8.5 cm range itself.
  • Treating the figure as a promise. A child commonly ends up anywhere in the 17 cm range, and the range is a typical spread, not a limit.
  • Using self-reported or rounded parent heights. People often overstate their height by a centimetre or two, which carries into the result.
  • Applying it to a child whose parents come from very different backgrounds or who has a medical growth condition. The method is a simple average and does not account for these.

Sources

About this calculator

The mid-parental height method is a widely used pediatric estimate of a child's likely adult height, based on the simple observation that height is strongly heritable. The formula averages both parents' heights and applies a fixed adjustment for the child's sex — adding about 6.5 cm for boys and subtracting about 6.5 cm for girls — to account for the average height difference between men and women.

This calculator takes both parents' heights and the child's sex and returns the predicted adult height along with the expected ±8.5 cm range that reflects normal biological variation around the estimate. It's used by pediatricians and pediatric endocrinologists as a rough benchmark when tracking a child's growth curve — a child growing well outside their predicted range can be a signal to investigate growth hormone or other endocrine issues — though it remains an estimate, not a guarantee, since genetics beyond the parents and environmental factors also play a role.

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Comments (1)

  • Editorial team

    Treat the figure as a target for the family, not a forecast for one child. Parents of 170 and 160 cm with a girl give 158.5 cm, and the tool's band runs from 150.0 to 167.0 cm. Use measured heights rather than remembered ones, and compare the child's own growth curve with it. A child who keeps crossing growth-chart lines downward is a reason to talk to a doctor. Would a version that uses a child's current percentile help?

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