# 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.

- Calculator id: `child-height-predictor` · Category: Health (`health`) · Tool name: `predict_adult_height`
- Canonical page: https://tttkmbb.com/health/child-height-predictor · This document: https://tttkmbb.com/health/child-height-predictor.md · JSON definition: https://tttkmbb.com/health/child-height-predictor.json

## Purpose

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.

**Use when:** 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.

## Input

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

## Output

| Field | 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. |

## 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.

## Data Sources

- Tanner JM, Goldstein H, Whitehouse RH (1970) Standards for children's height at ages 2–9 years allowing for height of parents, Arch Dis Child 45:755-762 — https://adc.bmj.com/content/45/244/755 (peer_reviewed, retrieved 2026-09-24)
- Wikipedia – Human height (predicting adult height) — https://en.wikipedia.org/wiki/Human_height (reference, retrieved 2026-09-24)

Data freshness: `static`. Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output.

## API

- `GET https://tttkmbb.com/api/v1/calculate/child-height-predictor?mother_height_cm=…&father_height_cm=…&sex=…`
- `POST https://tttkmbb.com/api/v1/calculate/child-height-predictor` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/child-height-predictor · OpenAPI operationId `predict_adult_height` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool:  `run_calculator` with `{"calculator_id": "child-height-predictor", "inputs": {…}}`

## Example

- Boy, mother 165 cm, father 180 cm: inputs `{"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: inputs `{"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
```

## Limitations

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. 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. All values are computed from the formula above; no measurement or live data is involved.

## 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

- [BMI Calculator](https://tttkmbb.com/health/bmi.md) — Adult BMI from the predicted height and a weight.
- [Ideal Weight Calculator](https://tttkmbb.com/health/ideal-weight.md) — Ideal-weight formulas for the predicted adult height.