# Ideal Weight Calculator

> Computes ideal body weight from height and sex with the four common clinical formulas (Devine, Robinson, Miller, Hamwi) and the BMI 18.5–24.9 healthy range.

- Calculator id: `ideal-weight` · Category: Health (`health`) · Tool name: `calculate_ideal_weight`
- Canonical page: https://tttkmbb.com/health/ideal-weight · This document: https://tttkmbb.com/health/ideal-weight.md · JSON definition: https://tttkmbb.com/health/ideal-weight.json

## Purpose

Computes ideal body weight from height and sex with the four common clinical formulas (Devine, Robinson, Miller, Hamwi) and the BMI 18.5–24.9 healthy range.

**Use when:** You need a reference 'ideal' weight for an adult, e.g. for drug dosing (Devine) or general guidance, or the healthy weight range for a height.

**Do not use when:** The person is under 18 or you need body-composition targets; the formulas are population averages, not individual prescriptions.

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `sex` | enum: male \| female |  | required | Biological sex used to select the formula coefficients. |
| `height_cm` | number | cm | required | Height in centimetres. Formulas are defined for heights above 152.4 cm (5 ft). (min 120, max 260) |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `devine_kg` | number | kg | Most widely used in pharmacology. |
| `robinson_kg` | number | kg | Robinson et al. modification. |
| `miller_kg` | number | kg | Miller et al. modification. |
| `hamwi_kg` | number | kg | Hamwi method. |
| `healthy_bmi_range_min_kg` | number | kg | Weight at BMI 18.5. |
| `healthy_bmi_range_max_kg` | number | kg | Weight at BMI 24.9. |

## Formula

`With h = inches over 5 ft (60 in): Devine male 50 + 2.3h, female 45.5 + 2.3h; Robinson male 52 + 1.9h, female 49 + 1.7h; Miller male 56.2 + 1.41h, female 53.1 + 1.36h; Hamwi male 48 + 2.7h, female 45.5 + 2.2h. For heights under 5 ft the same slope is applied downward.`

## Data Sources

- Pai MP, Paloucek FP (2000) The origin of the 'ideal' body weight equations, Ann Pharmacother 34:1066-1069 — https://pubmed.ncbi.nlm.nih.gov/10981254/ (peer_reviewed, retrieved 2026-09-23)
- WHO – A healthy lifestyle: body mass index — https://www.who.int/europe/news-room/fact-sheets/item/a-healthy-lifestyle---who-recommendations (standard, retrieved 2026-09-23)

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/ideal-weight?sex=…&height_cm=…`
- `POST https://tttkmbb.com/api/v1/calculate/ideal-weight` 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/ideal-weight · OpenAPI operationId `calculate_ideal_weight` 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": "ideal-weight", "inputs": {…}}`

## Example

- Male, 175 cm: inputs `{"sex":"male","height_cm":175}` → `{"devine_kg":70.5,"robinson_kg":68.9,"miller_kg":68.7,"hamwi_kg":72,"healthy_bmi_range_min_kg":56.7,"healthy_bmi_range_max_kg":76.3}`
- Female, 160 cm: inputs `{"sex":"female","height_cm":160}` → `{"devine_kg":52.4,"robinson_kg":54.1}`

```
GET https://tttkmbb.com/api/v1/calculate/ideal-weight?sex=male&height_cm=175
```

## Limitations

The person is under 18 or you need body-composition targets; the formulas are population averages, not individual prescriptions. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Why do the formulas disagree?**

Each was fitted to a different reference population and purpose (Devine for drug dosing, Hamwi for dietetics). Differences of 2–4 kg are normal; the BMI range is a broader, evidence-based guide.

**Is ideal weight the same as healthy weight?**

No. 'Ideal' formulas give a single point estimate; a healthy weight is any weight in the BMI 18.5–24.9 range for adults, with body composition taken into account.

## Related

- [BMI Calculator](https://tttkmbb.com/health/bmi.md) — Check where a current weight falls in the BMI categories.