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Child Height Predictor

Predicts a child's adult height from the parents' heights with the sex-adjusted mid-parental (target) height method of Tanner, Goldstein and Whitehouse (1970): boys (mother + father + 13 cm) / 2, girls (mother + father − 13 cm) / 2, with a ± 8.5 cm target range.

When to use

You want a genetic-potential estimate of a child's adult height from the parents' heights, or the target range against which a child's growth is judged.

Do not use when: You need a prediction that uses the child's own current height, bone age or growth percentile (use growth charts or the Khamis-Roche method); the estimate is informational only, not medical advice.

Formula

boys: predicted_height_cm = (mother_height_cm + father_height_cm + 13) / 2; girls: predicted_height_cm = (mother_height_cm + father_height_cm − 13) / 2; range_low_cm = predicted − 8.5; range_high_cm = predicted + 8.5

The 13 cm adjustment is the average adult height difference between men and women; the ± 8.5 cm range (about two standard deviations) contains roughly 95 % of the adult heights of children of the same parents. Nutrition, illness, puberty timing and measurement error are not modelled. Informational only, not medical advice.

Inputs

Parameter	Type	Unit	Required	Description
`mother_height_cm`	number	cm	yes	Biological mother's adult height in centimetres. Range: ≥ 120, ≤ 220
`father_height_cm`	number	cm	yes	Biological father's adult height in centimetres. Range: ≥ 120, ≤ 230
`sex`	enum: male \| female		yes	Sex of the child: boys add 13 cm, girls subtract 13 cm (the average adult male–female height difference) before halving.

Outputs

Output	Type	Unit	Description
`predicted_height_cm`	number	cm	Sex-adjusted mid-parental (target) height.
`range_low_cm`	number	cm	predicted_height_cm − 8.5 cm.
`range_high_cm`	number	cm	predicted_height_cm + 8.5 cm.
`predicted_height_ft_in`	string		The prediction in feet and inches, e.g. '5 ft 10.5 in'.
`method_note`	string		Which formula was applied and what the range means.

Example

Boy, mother 165 cm, father 180 cm: {"mother_height_cm":165,"father_height_cm":180,"sex":"male"} → {"predicted_height_cm":179,"range_low_cm":170.5,"range_high_cm":187.5,"predicted_height_ft_in":"5 ft 10.5 in"}

Girl, mother 165 cm, father 180 cm: {"mother_height_cm":165,"father_height_cm":180,"sex":"female"} → {"predicted_height_cm":166,"range_low_cm":157.5,"range_high_cm":174.5,"predicted_height_ft_in":"5 ft 5.4 in"}

GET https://tttkmbb.com/api/v1/calculate/child-height-predictor?mother_height_cm=165&father_height_cm=180&sex=male

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/child-height-predictor (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/child-height-predictor · Markdown: https://tttkmbb.com/health/child-height-predictor.md · JSON definition: https://tttkmbb.com/health/child-height-predictor.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="child-height-predictor"
OpenAPI operationId: predict_adult_height
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

How accurate is the mid-parental height?

About 95 % of children end up within ± 8.5 cm of the target, so a single prediction can easily be 5 cm off. Methods that use the child's current height and bone age (e.g. Khamis-Roche, Bayley-Pinneau) are more precise.

Why 13 cm?

Adult men are on average about 13 cm (5 in) taller than adult women, so the father's height is expressed on the female scale for girls and the mother's on the male scale for boys before averaging.

Related calculators

BMI Calculator — Adult BMI from the predicted height and a weight.
Ideal Weight Calculator — Ideal-weight formulas for the predicted adult height.