# Body Surface Area Calculator

> Computes body surface area in square metres from height and weight using the Mosteller and Du Bois formulas, as used for chemotherapy and other weight-independent dosing.

- Calculator id: `body-surface-area` · Category: Health (`health`) · Tool name: `calculate_body_surface_area`
- Canonical page: https://tttkmbb.com/health/body-surface-area · This document: https://tttkmbb.com/health/body-surface-area.md · JSON definition: https://tttkmbb.com/health/body-surface-area.json

## Purpose

Computes body surface area in square metres from height and weight using the Mosteller and Du Bois formulas, as used for chemotherapy and other weight-independent dosing.

**Use when:** You need BSA for drug dosing, cardiac index or physiological normalisation.

**Do not use when:** You need body composition or BMI; BSA does not indicate fatness.

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `weight_kg` | number | kg | required | Body weight in kilograms. (> 0, max 700) |
| `height_cm` | number | cm | required | Height in centimetres. (min 30, max 300) |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `bsa_mosteller_m2` | number | m² | √(height_cm × weight_kg / 3600). |
| `bsa_dubois_m2` | number | m² | 0.007184 × weight^0.425 × height^0.725. |
| `bsa_haycock_m2` | number | m² | 0.024265 × weight^0.5378 × height^0.3964 (often used in paediatrics). |

## Formula

`Mosteller: BSA = √(H·W / 3600). Du Bois: BSA = 0.007184 · W^0.425 · H^0.725. Haycock: BSA = 0.024265 · W^0.5378 · H^0.3964. H in cm, W in kg.`

## Data Sources

- Mosteller RD (1987) Simplified calculation of body-surface area, N Engl J Med 317:1098 — https://pubmed.ncbi.nlm.nih.gov/3657876/ (peer_reviewed, retrieved 2026-09-23)
- Du Bois D, Du Bois EF (1916) A formula to estimate the approximate surface area if height and weight be known, Arch Intern Med 17:863-871 — https://pubmed.ncbi.nlm.nih.gov/2520314/ (peer_reviewed, 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/body-surface-area?weight_kg=…&height_cm=…`
- `POST https://tttkmbb.com/api/v1/calculate/body-surface-area` 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/body-surface-area · OpenAPI operationId `calculate_body_surface_area` 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": "body-surface-area", "inputs": {…}}`

## Example

- 70 kg, 175 cm: inputs `{"weight_kg":70,"height_cm":175}` → `{"bsa_mosteller_m2":1.845,"bsa_dubois_m2":1.847,"bsa_haycock_m2":1.85}`

```
GET https://tttkmbb.com/api/v1/calculate/body-surface-area?weight_kg=70&height_cm=175
```

## Limitations

You need body composition or BMI; BSA does not indicate fatness. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Which formula do hospitals use?**

Mosteller is the most common because it is simple and within 1–2% of Du Bois for adults; Haycock is favoured for infants and children.

## Related

- [BMI Calculator](https://tttkmbb.com/health/bmi.md) — A different height–weight index used for weight classification.