Health & Fitness
Height Predictor Calculator
Use this height predictor calculator for an educational estimate of how tall a child may be as an adult, based only on the biological parents' heights.
It uses the mid-parental (Tanner) method, a genetics-only rule of thumb — it is not medical advice or a growth assessment, and real adult height also depends on nutrition, overall health, and the timing of puberty. Read the expected range first; the single midpoint number is not a promise.
Used by the formula: it shifts the mid-parental average up 13 cm for boys and down 13 cm for girls.
0 to 11.9 — carry every 12 inches into feet.
0 to 11.9 — carry every 12 inches into feet.
Try an example
Result
Predicted adult height (midpoint)
—
Population midpoint from parent heights alone — read it together with the range below, not as a promise.
- Expected range
- —
- Expected range (metric)
- —
- Midpoint
- —
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Study path
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What the height predictor calculator solves
This calculator estimates how tall a child may be as an adult using only the heights of the two biological parents. It uses the mid-parental method, also called the Tanner method — the same quick genetics-based estimate pediatricians use as a first reference point during growth checkups. Enter both parents' heights in centimeters or feet and inches, pick the child's sex, and read the predicted The point exactly halfway between two other points. together with the expected range.
Formula
The 13 cm term (about 5 in) is the average adult height difference between men and women. Adding it for boys and subtracting it for girls puts both parents' heights on the child's scale before averaging. Worked in inches, the same formula becomes the parents' average plus or minus 2.5 in, because half of 13 cm is 6.5 cm, or about 2.5 in. This calculator does all of its math in centimeters and converts for display, so the two unit modes always agree.
The range matters more than the single number. Under the standard clinical assumption behind the Tanner method, the midpoint +/- 8.5 cm spans roughly the 3rd to 97th percentile of expected adult heights for children of those parents — so most children land inside the band, and some still fall outside it.
How to use it
- Choose the child's sex — the formula shifts the mid-parental average up 13 cm for boys and down 13 cm for girls.
- Pick centimeters or feet + inches and enter each biological parent's height.
- Read the expected range first, then the midpoint; the range is the honest answer and the midpoint is just its center.
How to read the answer
Treat the midpoint as the center of a range, not a promise. Under the standard mid-parental assumption, most children of the same parents finish within about 8.5 cm (3.35 in) above or below the midpoint, and outliers happen in both directions. Nutrition, chronic illness, and early or late puberty can all move a child's real adult height, which is why this result is an educational estimate and not a medical assessment.
Common mistakes and edge cases
- Reading the midpoint as a guarantee — siblings with identical parents routinely end up several centimeters apart, which is why the +/- 8.5 cm range is shown first.
- Mixing units, such as measuring one parent in centimeters and the other in inches, or typing 5.11 to mean 5 ft 11 in.
- Entering 12 or more in the inches field — carry every 12 inches into feet, so 5 ft 13 in should be entered as 6 ft 1 in.
- Using the formula for a child with a suspected growth or hormonal condition; that calls for a pediatrician, growth charts, and possibly bone-age studies, not a genetics average.
- Applying it with adoptive or step-parent heights — the method only reflects the biological parents.
Worked examples
Boy with parents 5 ft 5 in and 5 ft 11 in
Heights convert to centimeters first, then the boy formula adds 13 cm before averaging.
Predicted adult height (midpoint)
5 ft 10.6 in (179.2 cm)
Girl with parents 165 cm and 180 cm
The girl formula subtracts 13 cm: (165 + 180 - 13) / 2 = 166 cm.
Predicted adult height (midpoint)
5 ft 5.4 in (166 cm)
Midpoint that rounds to a whole foot
A 182.8 cm midpoint is 71.97 in, which rounds up and carries into 6 ft 0 in.
Predicted adult height (midpoint)
6 ft 0 in (182.8 cm)
Girl with parents 5 ft 4 in and 6 ft 0 in
64 in and 72 in convert to 162.6 cm and 182.9 cm; the girl formula subtracts 13 cm before averaging: 166.2 cm.
Predicted adult height (midpoint)
5 ft 5.4 in (166.2 cm)
Out-of-range parent height
A 90 cm parent height is outside the supported adult range, so the calculator reports an error instead of a misleading prediction.
Predicted adult height (midpoint)
Error
Frequently asked questions
How accurate is the mid-parental (Tanner) height method?+
It is a rough genetic estimate, not a measurement. Under the standard clinical assumption, the midpoint +/- 8.5 cm covers roughly the 3rd to 97th percentile of adult heights for children of those parents, so most — but not all — children land inside the range. Clinicians who need real precision use growth charts over time and bone-age X-rays instead.
Why does the formula add or subtract 13 cm?+
13 cm (about 5 in) is the average adult height difference between men and women. Adding it for a boy converts the mother's height onto the male scale before averaging; subtracting it for a girl does the reverse. After dividing by 2, the shift works out to about 2.5 in, which is why the inch version of the formula is the parents' average plus or minus 2.5 in.
Is this a medical growth assessment?+
No. It is an educational estimate from parental genetics only. It cannot detect growth disorders and is not medical advice. A pediatrician tracks a child's height percentile over time and can order bone-age studies when there is a genuine concern about growth.
Can a child end up outside the predicted range?+
Yes. The range is a statistical band, not a boundary. Nutrition, chronic illness, sleep, and the timing of puberty all influence growth, and some children simply fall outside the expected band for genetic reasons a two-input formula cannot capture.
Does the child's current height matter?+
The mid-parental formula ignores the child's current height entirely. If a child has held a consistent percentile on a growth chart for years, projecting along that percentile is often a better everyday predictor than the parental average — and it is exactly what pediatricians look at.
About this calculator
- Written by
- mathcheck editorial team
- Last reviewed
- September 4, 2026
Method
- Uses the Tanner mid-parental method: boys (mother + father + 13 cm) / 2, girls (mother + father - 13 cm) / 2, with all math done in centimeters and converted for display.
- The 13 cm sex adjustment reflects the average adult height difference between men and women (about 5 in; roughly +/- 2.5 in after halving when working in inches).
- The expected range is modeled as the midpoint +/- 8.5 cm (+/- 3.35 in), the commonly cited clinical target-height band, often described as spanning roughly the 3rd to 97th percentile.
- Genetics-only estimate: nutrition, chronic health conditions, sleep, and pubertal timing are not modeled, and output is educational, not medical advice.
References
- Mid-parental (Tanner) target height — Pediatric references describe target adult height as the sex-adjusted mid-parental average (+/- 13 cm adjustment) with an expected band of about +/- 8.5 cm, following Tanner and colleagues' growth work.
- Expected-range assumption — The +/- 8.5 cm band is the standard clinical rule of thumb for mid-parental target height and is commonly presented as covering roughly the 3rd to 97th percentile of outcomes; it is an assumption, not a guarantee for any individual child.
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Last updated: September 4, 2026