Height Calculator
Predict a child's adult height from the parents' heights with the Tanner mid-parental formula, including the ±8.5 cm target range and what it cannot tell you.
Height Calculator: with the default inputs, predicted adult height is 5.8 ft.
The mid-point of the target range — a central estimate, not a forecast.
- Target range, from
- 5.52 ft
- Target range, to
- 6.08 ft
- Predicted height in feet and inches
- 5' 9.6"
- Target range in feet and inches
- 5' 6.2" to 6' 0.9"
- Plain mid-parental height
- 5.58 ftThe simple average of the parents, before the 13 cm sex correction.
- Width of the target range
- 6.7 inHow wide the honest answer is.
Assumptions
- Uses the Tanner, Goldstein & Whitehouse (1970) mid-parental target height with a 13 cm sex correction and a ±8.5 cm target range representing within-family variance.
- The ±8.5 cm range is contested: Tanner later used ±9 cm for girls and ±10 cm for boys, and the AAFP uses a flat ±10 cm. Treat any of them as a soft guide, not a cut-off.
- The Ogata (1990) option adds 2 cm for the secular trend and uses ranges of ±9 cm for boys and ±8 cm for girls.
- Both formulas were derived from specific populations — English and Japanese respectively — and the sex correction differs between populations.
- The child's own height, age, bone age, pubertal stage, nutrition and medical history are not inputs and matter more than this arithmetic.
- This is an estimate of a range, not a diagnosis, and it is not a substitute for growth monitoring by a clinician.
| Formula | Predicted | Range | Source |
|---|---|---|---|
| Tanner (1970) | 176.7 cm — 5' 9.6" | 5' 6.2" to 6' 0.9" | Arch Dis Child, English children |
| Ogata (1990) | 178.7 cm — 5' 10.3" | 5' 6.8" to 6' 1.9" | Japanese data, adds 2 cm for the secular trend |
Both use the same mid-parental step with a 13 cm sex correction. Neither was derived from your child's population, and the correction factor is known to vary between populations.
How this is worked out
The formula
Tanner target height (cm): Boy: (father + mother + 13) ÷ 2 Girl: (father + mother − 13) ÷ 2 Target range = target height ± 8.5 cm (Tanner, Goldstein & Whitehouse, 1970) Ogata (1990) variant: the same, plus 2 cm, with a range of ±9 cm for boys and ±8 cm for girls.
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Child's sex
- Choose one of 2 options.Boy · Girl
- Father's height
- A number.in ft, in, cm, m · from 3 to 8.5 · defaults to 5.8333
- Mother's height
- A number.in ft, in, cm, m · from 3 to 8.5 · defaults to 5.3333
- Formula(under More options)
- Choose one of 2 options.Tanner (1970) — the standard clinical formula · Ogata (1990) — Tanner plus 2 cm for the secular trend
What you get back
- Predicted adult heightmain answer
- The mid-point of the target range — a central estimate, not a forecast.
- Target range, from
- Target range, to
- Predicted height in feet and inches
- Target range in feet and inches
- Plain mid-parental height
- The simple average of the parents, before the 13 cm sex correction.
- Width of the target range
- How wide the honest answer is.
What this assumes
- Uses the Tanner, Goldstein & Whitehouse (1970) mid-parental target height with a 13 cm sex correction and a ±8.5 cm target range representing within-family variance.
- The ±8.5 cm range is contested: Tanner later used ±9 cm for girls and ±10 cm for boys, and the AAFP uses a flat ±10 cm. Treat any of them as a soft guide, not a cut-off.
- The Ogata (1990) option adds 2 cm for the secular trend and uses ranges of ±9 cm for boys and ±8 cm for girls.
- Both formulas were derived from specific populations — English and Japanese respectively — and the sex correction differs between populations.
- The child's own height, age, bone age, pubertal stage, nutrition and medical history are not inputs and matter more than this arithmetic.
- This is an estimate of a range, not a diagnosis, and it is not a substitute for growth monitoring by a clinician.
About this calculator
This is an estimate, not a diagnosis. It predicts a range a child is likely to land in, based only on how tall their parents are. It cannot tell you whether a child is growing normally, and nothing on this page should replace a paediatrician plotting real heights on a real growth chart.
What the Tanner formula does
Adult height is strongly heritable, so the simplest useful prediction is the average of the parents, shifted by the average difference between adult men and women. Tanner, Goldstein and Whitehouse published it in Archives of Disease in Childhood in 1970:
- Boy: (father's height + mother's height + 13 cm) ÷ 2
- Girl: (father's height + mother's height − 13 cm) ÷ 2
Around that mid-point they put a target range of ±8.5 cm, which represents the variation between siblings in the same family. That range is the important output. It is 17 cm wide — nearly seven inches — and it is that wide because the honest uncertainty is that large. A prediction reported as a single number is hiding this.
The width of that range is itself disputed. Tanner's original ±8.5 cm is what this calculator uses and what paediatric references most often quote as the 3rd-to-97th-centile band. Tanner later widened it to ±9 cm for girls and ±10 cm for boys, and the American Academy of Family Physicians' 2015 review of short and tall stature uses a flat ±10 cm for both. Nobody has settled it, and rigid cut-offs on either number are a known source of misdiagnosis.
What clinicians actually use it for
Not for predicting height. For a screening question: is this child growing within the range their family would predict? A child tracking well below their target range is the signal that prompts further investigation — growth hormone deficiency, coeliac disease, thyroid problems, chronic conditions. That is the entire clinical purpose. The precision of the mid-point barely matters for it.
Five reasons the number is soft
- Secular trend. Populations have grown taller since Tanner's English cohort was measured, so the formula tends to run slightly low. Ogata's 1990 variant, available under More options, adds 2 cm for this.
- The 13 cm correction is population-specific. It is roughly 13.9 cm in Italian data, 14.4 cm in Flemish data and 15.8 cm in Indian data. WHO growth charts imply about 13.3 cm.
- Assortative mating. The formula assumes partners tend to be similar in height. When the parents' heights are very different, it gets less reliable.
- Very short parents. The formula is known to underestimate adult height in children of very short parents — a real problem in clinics, because it makes growth-promoting treatments look more effective than they are.
- It ignores the child entirely. Bone age, pubertal timing, birth weight, nutrition and illness all matter, and none are inputs here. Bone-age methods such as Bayley-Pinneau and Khamis-Roche use the child's own measurements and do better, at the cost of needing an X-ray or repeated measurements.
How to read it
Take the range, not the mid-point. If someone lands anywhere inside it, the formula was right. If a child is consistently tracking outside it — especially below — that is worth a paediatric appointment, not a recalculation.
And it is worth saying: this predicts a measurement, not a life. Height is not a target to hit, and nothing about a child's development is settled by a number that came out of averaging their parents.
Frequently asked questions
▸How tall will my child be?
Average the parents' heights, then add 13 cm for a boy or subtract 13 cm for a girl, and divide by two. Then treat the answer as the centre of a range about 17 cm wide — that width is the real answer.
▸How accurate is the mid-parental height formula?
It gives a target range that most children land inside, but the range is ±8.5 cm. As a point prediction it is weak, and it underestimates for children of very short parents. Bone-age methods using the child's own measurements are more accurate.
▸Why is there a 13 cm adjustment?
It is the average difference in adult height between men and women in Tanner's English data. That gap varies between populations — closer to 14 cm in some European data and 16 cm in some Indian data — which is one reason the formula travels imperfectly.
▸Can a child grow taller than the prediction?
Easily. The range covers most children, not all, and better nutrition and health across generations mean children often exceed what their parents' heights suggest. This is a family average, not a ceiling.
▸When should I see a doctor about a child's height?
If a child is consistently tracking well below the target range, if their growth rate slows or crosses downward through percentile lines, or if puberty is very early or very late. Serial measurements on a growth chart are what matter, not one calculation.
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