What is mid-parental height?
Mid-parental height is a simple genetics-based estimate that averages both parents' heights and adjusts for the roughly 13 cm average height gap between adult men and women. It was developed by auxologist James Tanner as a rough guide to a child's growth potential, not a precise forecast.
Boy: (father's height + mother's height + 13 cm) ÷ 2 · Girl: (father's height + mother's height − 13 cm) ÷ 2
How accurate is this?
This estimate reflects genetic potential only. Actual adult height is also shaped by nutrition, health, sleep, and the timing of puberty, so real outcomes commonly land several centimeters away from the midpoint — that is why the ±8.5 cm range matters more than the single number.
How to predict a child's adult height
The mid-parental height method estimates a child's adult height from both parents' heights. Add the mother's and father's height, adjust by about 13 cm for the average sex difference, then divide by two. The result is a genetic estimate, not a guarantee — actual height commonly lands ±8.5 cm on either side.
Steps
- Measure or confirm both parents' height in cm (or ft/in — the calculator converts automatically).
- Select the child's sex, since boys and girls use a different adjustment.
- Add the father's and mother's height together.
- Add 13 cm for a boy, or subtract 13 cm for a girl, then divide the total by two.
- Read the predicted height plus the ±8.5 cm likely range — most children land somewhere inside that range, not exactly on the midpoint.
Formula
Boy: (father's height + mother's height + 13 cm) / 2 Girl: (father's height + mother's height − 13 cm) / 2 Target range: predicted height ± 8.5 cm
- father's height, mother's height — each parent's own measured adult height, in cm
- 13 cm — the average height difference between adult men and women, used to adjust for the child's sex
- ± 8.5 cm — the range covering roughly the 3rd–97th percentile of outcomes, based on Tanner's original estimate
Example: predicted height by parent height
| Father | Mother | Boy — predicted (range) | Girl — predicted (range) |
|---|
| 170 cm | 158 cm | 170.5 cm (162.0–179.0 cm) | 157.5 cm (149.0–166.0 cm) |
| 175 cm | 162 cm | 175.0 cm (166.5–183.5 cm) | 162.0 cm (153.5–170.5 cm) |
| 178 cm | 165 cm | 178.0 cm (169.5–186.5 cm) | 165.0 cm (156.5–173.5 cm) |
| 180 cm | 168 cm | 180.5 cm (172.0–189.0 cm) | 167.5 cm (159.0–176.0 cm) |
| 165 cm | 155 cm | 166.5 cm (158.0–175.0 cm) | 153.5 cm (145.0–162.0 cm) |
FAQ
How accurate is this prediction, really?
Mid-parental height explains a large share of a child's height potential, but studies comparing predicted to actual adult height find gaps of several centimeters are common, and the method was validated on specific populations decades ago — it may under- or overestimate height in other groups. Treat the number as a rough range, not a guarantee.
Can a child end up taller than both parents?
Yes. The predicted height is a midpoint, and roughly half of children finish above it. Nutrition, health, sleep, and how early or late puberty starts all push real height above or below the genetic estimate.
What height should I enter for the parents?
Use each parent's own adult height, measured after they stopped growing (typically the late teens), not a height from childhood.
Does this work the same for every ethnic group?
The 13 cm adjustment and the ±8.5 cm range come from research on specific populations. Average height and the sex gap vary somewhat by ethnicity and country, so treat the result as a general estimate rather than one tuned to a specific population.
My child's growth seems off — should I be concerned?
This calculator only estimates a long-term target, not current growth. If a child's growth curve flattens suddenly or crosses percentile lines on a pediatric growth chart, talk to a pediatrician rather than relying on this estimate.
Mid-parental height is a rough genetic estimate developed decades ago by researcher James Tanner from a limited population sample — it is not a medical prediction, and it does not account for nutrition, chronic illness, hormonal conditions, or how early or late puberty starts, any of which can push adult height well outside the ±8.5 cm range. For tracking how a young child is actually growing over time, a growth percentile chart is more useful than a single adult-height estimate; utilduck's child growth percentile tool (/tools/child-growth-percentile.html, coming soon) will cover that. If you have any concern about a child's growth, consult a pediatrician.
Sources: Accuracy of self-reported height measurements in parents and its effect on mid-parental target height calculation (PMC), Accurate Prediction of Children's Target Height from Their Mid-Parental Height (PMC)