Child Height Predictor Calculator
Example: Boy, 10y, 140 cm, 32 kg → about 178 cm
Estimate a child’s adult height by two published methods. Khamis-Roche uses the child’s own height, weight and age alongside the parents’ heights and is the more accurate of the two. The mid-parental formula, also known as Tanner’s target height, needs only the parents’ heights. Neither is a promise, and the range matters more than the number.
Calculation results updated
Target range and parent heights
Predicted Adult Height
Lower Estimate
Upper Estimate
Method Used
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How to use this calculator
- Choose metric or imperial units.
- Select the child's sex. This decides whether the 13 cm adjustment is added or subtracted.
- Enter both biological parents' measured adult heights. Measured beats remembered; self-reported heights tend to run high.
- Read the target height and the range around it. The range matters more than the single number.
- Treat the result as a family reference point. If you are worried about a child's growth, serial measurements plotted on a growth chart by a clinician are the thing that actually answers the question.
How We Calculate This
Khamis-Roche predicts adult stature as b0 + b1×(child’s height) + b2×(child’s weight) + b3×(parents’ mean height), with coefficients specific to each half-year of age from 4.0 to 17.5 and to sex. The published regression is in inches and pounds, so metric entries are converted before and after, and coefficients between half-year steps are linearly interpolated. Its mid-parent term is the plain average of the parents, with no sex adjustment, because sex is handled by the coefficient table. Reported error is about 5.6 cm for boys and 4.3 cm for girls. Mid-parental target height is (mother + father + 13 cm) ÷ 2 for boys and (mother + father − 13 cm) ÷ 2 for girls. This is Tanner’s target height formula: Tanner stated it as the parents’ average plus 6.5 cm for boys or minus 6.5 cm for girls, which is the same arithmetic. The displayed range is ±10.2 cm (±4 in), following AAP educational material. Tanner’s original 1970 range was ±8.5 cm, later revised to ±9 cm for girls and ±10 cm for boys, so published ranges differ by source. This is a familial reference, not a validated individualized prediction or treatment tool.
Methodology last reviewed: July 2026. How SparkCalc works
Sources: American Academy of Pediatrics: Mid-Parental Height · Khamis and Roche 1994 method record · American Academy of Pediatrics: corrected Khamis-Roche tables erratum (1995) · Harry Khamis, Wright State University: stature prediction error margins · Accurate Prediction of Children’s Target Height from Their Mid-Parental Height (Tanner’s formula and target ranges)
Tanner's formula and mid-parental height are the same calculation
These are two names for one method, which causes a lot of confusion. Tanner and colleagues described target height in 1970 as the average of the parents' heights, plus 6.5 cm for a boy or minus 6.5 cm for a girl. The mid-parental formula is usually written as (mother + father + 13) ÷ 2 for boys and (mother + father − 13) ÷ 2 for girls. Those are algebraically identical. Adding 13 cm before halving is the same as adding 6.5 cm after. So if you arrived here searching for the Tanner formula, the calculator above performs it. Where sources genuinely disagree is the range, not the centre. Tanner's original paper put the expected span at ±8.5 cm, framed as the 3rd to 97th percentile. He later widened it to ±9 cm for girls and ±10 cm for boys. AAP material uses ±4 inches, or ±10.2 cm, which is what this calculator displays. Later work using a ±1.64 SDS interval under CDC standards arrives at roughly ±10.6 cm for girls and ±11.7 cm for boys. One reason the newer ranges run wider is that Tanner's cutoffs were derived from children who had not finished growing, rather than from measured adult heights within nuclear families.
Choosing between Khamis-Roche and mid-parental height
The two methods answer different questions. Mid-parental height asks where a family's genetic midpoint sits. It needs only the parents and can be worked out before a child is born. Khamis-Roche asks where this particular child is likely to end up given how they are growing right now, so it needs the child measured. Use Khamis-Roche when you can. It combines the child's current height and weight with the parents' mean height, using coefficients that change every half-year of age and differ by sex, so it responds to whether a child is tracking tall, short, heavy or light for their age. Its published error is about 5.6 cm for boys and 4.3 cm for girls, against roughly 10 cm for a mid-parental target range. Use mid-parental when the child is under 4 or over 17.5, where the Khamis-Roche coefficients are not defined, when the child has not been born, or when you simply do not have their measurements to hand. Two caveats apply to Khamis-Roche whoever implements it. The coefficients published in 1994 contained an error corrected by a 1995 erratum, and both sets still circulate online, so a tool that does not say which it uses may be running the uncorrected numbers. And the coefficients come from the Fels Longitudinal Study, a cohort that is American, largely Caucasian, under-represents lower socioeconomic groups and has been recruiting since 1929, so accuracy in populations unlike that cohort is less well established.
What this estimate cannot do
It uses two numbers and a sex adjustment. It does not know the child's current height or weight, their stage of puberty, their nutrition, their health, their ancestry, or whether either parent's own growth was affected by illness or circumstance. A late developer and an early developer with identical parents get identical output. The range is the honest part of the result. A ±10 cm band is roughly 8 inches wide, and adult height still lands outside it often enough to matter. Treat the centre as the middle of a broad family expectation and nothing more. It also cannot detect a problem. Growth concerns are identified by plotting a child's measurements over time and watching whether they track along a percentile or cross downward through them. A single predicted number cannot show that pattern, and a reassuring result here is not evidence that growth is normal. If something seems off, serial measurements taken by a clinician are the answer.
Target height by parents’ heights
Mid-parental target height for the most commonly asked parent height combinations, using (mother + father ± 13 cm) ÷ 2. Figures are rounded to the nearest centimetre.
| Father | Mother | Boy | Girl |
|---|---|---|---|
| 5 ft 7 in (170 cm) | 4 ft 11 in (150 cm) | 167 cm (5 ft 5.5 in) | 154 cm (5 ft 0.5 in) |
| 5 ft 7 in (170 cm) | 5 ft 1 in (155 cm) | 169 cm (5 ft 6.5 in) | 156 cm (5 ft 1.5 in) |
| 5 ft 7 in (170 cm) | 5 ft 2 in (157 cm) | 170 cm (5 ft 7 in) | 157 cm (5 ft 2 in) |
| 5 ft 8 in (173 cm) | 5 ft 3 in (160 cm) | 173 cm (5 ft 8 in) | 160 cm (5 ft 3 in) |
| 5 ft 10 in (178 cm) | 5 ft 4 in (163 cm) | 177 cm (5 ft 9.5 in) | 164 cm (5 ft 4.5 in) |
| 5 ft 11 in (180 cm) | 5 ft 2 in (157 cm) | 175 cm (5 ft 9 in) | 162 cm (5 ft 4 in) |
| 5 ft 11 in (180 cm) | 5 ft 4 in (163 cm) | 178 cm (5 ft 10 in) | 165 cm (5 ft 5 in) |
| 6 ft 0 in (183 cm) | 5 ft 5 in (165 cm) | 180 cm (5 ft 11 in) | 167 cm (5 ft 5.5 in) |
| 6 ft 2 in (188 cm) | 5 ft 6 in (168 cm) | 184 cm (6 ft 0.5 in) | 171 cm (5 ft 7.5 in) |
| 6 ft 3 in (191 cm) | 5 ft 7 in (170 cm) | 187 cm (6 ft 1.5 in) | 174 cm (5 ft 8.5 in) |
Each figure carries a target range of roughly ±10.2 cm (±4 in). Adult height frequently falls outside it. This is a family reference, not a prediction for an individual child.
Which constant comes from which source
Published mid-parental height figures differ because they come from different papers. This is what each number is and where it originates.
| Value | What it is | Source |
|---|---|---|
| ±13 cm | Sex adjustment applied before halving, equal to ±6.5 cm on the parents’ average | Tanner et al., 1970 |
| ±6.5 cm | The same sex adjustment, stated as an offset from the parents’ mean height | Tanner et al., 1970 |
| ±8.5 cm | Original target range, 3rd to 97th percentile | Tanner et al., 1970 |
| ±9 cm girls, ±10 cm boys | Tanner’s later revision of the target range | Tanner, revised |
| ±10.2 cm (±4 in) | Target range used by this calculator | American Academy of Pediatrics |
| ±10.6 cm girls, ±11.7 cm boys | A ±1.64 SDS interval under CDC standards | Subsequent literature |
Tanner’s cutoffs were derived from measurements of children who had not finished growing, rather than from adult heights in nuclear families, which is one reason later ranges are wider.
Key terms
- Mid-parental height
- The average of both parents' heights, adjusted for the child's sex: add 13 cm for a boy or subtract 13 cm for a girl, then halve. It estimates the centre of a family's genetic height range.
- Tanner's formula
- The same calculation under a different name. Tanner stated it as the parents' mean height plus 6.5 cm for boys or minus 6.5 cm for girls, which is arithmetically identical to (mother + father ± 13) ÷ 2.
- Target range
- The band around the target height inside which most children in a family land. This calculator uses ±10.2 cm following AAP material. Tanner originally gave ±8.5 cm. It is a population reference band, not an individual confidence interval.
- Khamis-Roche method
- A prediction method that uses the child's own current height and weight alongside the parents' mean height, with coefficients that vary by age and sex. Defined for ages 4.0 to 17.5. More accurate than a parental average because it knows how the child is actually growing.
Frequently Asked Questions
How is mid-parental target height calculated?
For a boy: (mother’s height + father’s height + 13 cm) ÷ 2. For a girl: (mother’s height + father’s height − 13 cm) ÷ 2. The 13 cm adjustment is made before dividing; it is equivalent to about ±6.5 cm from the parents’ simple average.
Which method should I choose?
Khamis-Roche if the child is between 4 and 17.5 and you can measure their height and weight, because using the child’s own growth makes it more accurate than parental heights alone. Its published error is about 5.6 cm for boys and 4.3 cm for girls. Choose mid-parental, also called Tanner’s target height, if the child is outside that age range, has not been born yet, or you only know the parents’ heights.
Is this the Tanner formula?
Yes. Tanner’s target height formula is the mid-parental height plus 6.5 cm for a boy or minus 6.5 cm for a girl, which is arithmetically identical to (mother + father ± 13 cm) ÷ 2. The two names describe the same calculation, and this calculator performs it.
Why do sources quote 8.5 cm, 10 cm and 10.2 cm for the target range?
Because they come from different papers. Tanner’s original 1970 range was ±8.5 cm, corresponding to the 3rd and 97th percentiles. He later revised it to ±9 cm for girls and ±10 cm for boys. American Academy of Pediatrics material uses ±4 inches (±10.2 cm). Others use a ±1.64 SDS interval, about ±10.6 cm for girls and ±11.7 cm for boys under CDC standards. This calculator shows ±10.2 cm and labels it as an AAP reference range.
What are the limitations, and can it predict an exact height?
No, it cannot predict an exact height, before or after birth. It uses only parental heights and a sex adjustment, so it does not model the child’s own measurements, puberty timing, health, nutrition, ancestry or measurement error. Adult height can fall outside the range, and the estimate cannot diagnose abnormal growth. Growth concerns require serial measurements and professional assessment.
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Educational estimate only. Do not use it to diagnose growth, decide on testing or treatment, or reassure yourself about a concerning growth pattern. A pediatric healthcare professional can assess serial measurements and individual context.
References
- American Academy of Pediatrics: Mid-Parental Height
- Khamis and Roche 1994 method record
- American Academy of Pediatrics: corrected Khamis-Roche tables erratum (1995)
- Harry Khamis, Wright State University: stature prediction error margins
- Accurate Prediction of Children’s Target Height from Their Mid-Parental Height (Tanner’s formula and target ranges)