Height Predictor Calculator
Estimate a child’s target adult height range from both parents’ heights, using the mid-parental method of Tanner and colleagues.
Result
Enter father’s height and mother’s height to see the result.
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How to use the Height Predictor Calculator
- Choose the equation for a boy or a girl. Tanner's method adjusts one parent's height by the average difference between adult men and women, so the child's sex decides which way.
- Enter the father's and mother's heights, measured as adults, in feet and inches or centimetres.
- Read the target height and the range around it. It spans the 3rd to 97th centile, so most children with parents of those heights would be expected to fall inside it.
The mid-parental method
In 1970 James Tanner, Harvey Goldstein and Reginald Whitehouse published height standards for children that allow for the parents’ heights. Alongside them they described a quick way to mark a child’s “target” adult height: take both parents’ heights, adjust one of them for the difference between adult men and women, and find the midpoint.
boy's target = (father + mother + 13 cm) ÷ 2girl's target = (father − 13 cm + mother) ÷ 2range = target ± 8.5 cmThe 13 cm is the mean adult sex difference, about 5 inches. The 8.5 cm either side comes from Tanner’s reasoning: the 3rd to 97th centile range of mid-parent height is about 20 cm, and with a parent-child correlation of about 0.5 the corresponding range for a child is about 17 cm.
Reading the result
Tanner described the method as plotting the parents on a growth chart and reading off the midpoint of their centiles. The arithmetic here is the common way of doing the same thing in centimetres or inches. Either way the result is a range for where a child’s genes point, useful for a doctor watching a child’s growth, not a forecast.
Two things push real outcomes around. Children do not simply inherit the average of their parents, so tall parents often have children a little shorter than themselves and short parents children a little taller. And Tanner noted that if the parents grew up in poorer conditions than their child, the method will tend to predict too low.
What this page does not do
It does not use the child’s current height, age or bone age, and it is not a growth chart. Methods that predict an individual child’s adult height from their own measurements need reference tables and clinical measurement, and they are outside the scope of this calculator.
With your numbers
- The range is 8.5 cm either side: 66.2 in to 72.9 in
- (70 in + 64 in + 5.1 in) ÷ 2 = 69.6 in
Quick reference
A range from the parents’ heights, not a prediction for one child. If the parents grew up in harder circumstances than the child, Tanner notes the range may run low.
| Example | Target adult height |
|---|---|
| Boy, parents 5 ft 10 in and 5 ft 4 in | 69.6 in |
| Girl, parents 5 ft 10 in and 5 ft 4 in | 64.4 in |
| Boy, parents 6 ft 0 in and 5 ft 6 in | 71.6 in |
| Boy, parents 178 cm and 165 cm | 178 cm |
| Girl, parents 178 cm and 165 cm | 165 cm |
| Girl, parents 185 cm and 170 cm | 171 cm |
Common questions about the Height Predictor Calculator
- How accurate is this?
- It gives a range, and the range is the answer. Tanner and colleagues set it at 8.5 cm either side of the target, the span from the 3rd to the 97th centile for a child whose parents' heights are known. No single figure is likely to be exactly right; the range is what the method supports.
- Why add or subtract 13 cm?
- Men are on average taller than women. To put both parents on the same scale as the child, the method adds 13 cm, the mean adult sex difference Tanner used, to the mother's height for a boy, or takes it off the father's height for a girl, and then averages the two.
- Does it work for any child?
- It is a population method built on British and European longitudinal studies. It says nothing about an individual child's health, growth rate or the timing of puberty, and it does not use the child's own height. If you are concerned about how a child is growing, a doctor or health visitor can plot the child's measurements on a growth chart over time, which tells you far more than the parents' heights can.
- What if the parents are older?
- Height shrinks a little in later life. Tanner suggested adding about 1.5 cm to a parent measured between 45 and 55 and about 3 cm above 55, and using the best young adult height when only a reported height is available. This page does not make that correction for you; enter the corrected height if it applies.
- Can I use it for an adopted child?
- No. The method rests on the inheritance of height from the biological parents. Without their heights it has nothing to work from.