# Adjusted Body Weight Calculator

> Computes ideal body weight (Devine) and adjusted body weight (IBW + 0.4 × (actual − IBW)) used for drug dosing and creatinine clearance in people whose weight exceeds 120% of ideal.

- Calculator id: `adjusted-body-weight` · Category: Medical & Clinical (`medical`) · Tool name: `calculate_adjusted_body_weight`
- Canonical page: https://tttkmbb.com/medical/adjusted-body-weight · This document: https://tttkmbb.com/medical/adjusted-body-weight.md · JSON definition: https://tttkmbb.com/medical/adjusted-body-weight.json

## Purpose

Computes ideal body weight (Devine) and adjusted body weight (IBW + 0.4 × (actual − IBW)) used for drug dosing and creatinine clearance in people whose weight exceeds 120% of ideal.

**Use when:** You need the dosing weight for hydrophilic drugs (e.g. aminoglycosides) or the Cockcroft-Gault weight in an overweight adult.

**Do not use when:** The drug is dosed on actual weight (many lipophilic drugs), the person is under 18 or shorter than 152 cm, where Devine's formula is not validated.

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `sex` | enum: male \| female |  | required | Sex used to select the formula coefficients or thresholds. |
| `height_cm` | number | cm | required | Height in centimetres. (min 120, max 260) |
| `weight_kg` | number | kg | required | Actual body weight in kilograms. (> 0, max 700) |
| `correction_factor` | number |  | optional, default 0.4 | Fraction of the excess weight added to IBW; 0.4 is standard, some protocols use 0.3. (min 0.2, max 0.5) |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `ideal_body_weight_kg` | number | kg | 50 kg (male) or 45.5 kg (female) + 2.3 kg per inch over 5 ft. |
| `percent_of_ideal` | number | % | weight_kg / IBW × 100. |
| `adjusted_body_weight_kg` | number | kg | IBW + factor × (actual − IBW). |
| `adjusted_weight_applies` | boolean |  | True when actual weight exceeds 120% of ideal. |
| `dosing_weight_kg` | number | kg | Adjusted weight when it applies, otherwise actual weight. |
| `weight_basis` | string |  | Which weight the suggestion uses and why. |

## Formula

`IBW = 50 (male) or 45.5 (female) + 2.3 × (height_cm / 2.54 − 60); adjusted_BW = IBW + correction_factor × (weight_kg − IBW), applied when weight_kg > 1.2 × IBW`

The 0.4 factor assumes about 40% of excess adipose tissue is water and drug-distributing; it is a convention from aminoglycoside pharmacokinetics rather than a universal rule, and drug-specific labelling takes precedence. Results are informational only and not a substitute for clinical judgement or medical advice.

## 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 2026-09-24)
- Winter MA et al. (2012) Impact of various body weights and serum creatinine concentrations on the bias and accuracy of the Cockcroft-Gault equation, Pharmacotherapy 32:604-612 — https://pubmed.ncbi.nlm.nih.gov/22576791/ (peer_reviewed, 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/adjusted-body-weight?sex=…&height_cm=…&weight_kg=…`
- `POST https://tttkmbb.com/api/v1/calculate/adjusted-body-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/adjusted-body-weight · OpenAPI operationId `calculate_adjusted_body_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": "adjusted-body-weight", "inputs": {…}}`

## Example

- Male, 175 cm, 100 kg: inputs `{"sex":"male","height_cm":175,"weight_kg":100}` → `{"ideal_body_weight_kg":70.5,"percent_of_ideal":141.9,"adjusted_body_weight_kg":82.3,"adjusted_weight_applies":true,"dosing_weight_kg":82.3}`
- Female, 160 cm, 60 kg: inputs `{"sex":"female","height_cm":160,"weight_kg":60}` → `{"ideal_body_weight_kg":52.4,"percent_of_ideal":114.5,"adjusted_weight_applies":false,"dosing_weight_kg":60}`

```
GET https://tttkmbb.com/api/v1/calculate/adjusted-body-weight?sex=male&height_cm=175&weight_kg=100
```

## Limitations

The drug is dosed on actual weight (many lipophilic drugs), the person is under 18 or shorter than 152 cm, where Devine's formula is not validated. The 0.4 factor assumes about 40% of excess adipose tissue is water and drug-distributing; it is a convention from aminoglycoside pharmacokinetics rather than a universal rule, and drug-specific labelling takes precedence. Results are informational only and not a substitute for clinical judgement or medical advice. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Why 120% of ideal?**

Below that, the difference between actual and adjusted weight is small; most references (and the Winter 2012 analysis) start using adjusted weight around 120–130% of IBW.

**What if actual weight is below ideal?**

Actual weight is used for dosing; the adjusted-weight formula is not meant for underweight patients.

## Related

- [Ideal Weight Calculator](https://tttkmbb.com/health/ideal-weight.md) — Ideal weight by Devine, Robinson, Miller and Hamwi.
- [Creatinine Clearance Calculator](https://tttkmbb.com/medical/creatinine-clearance.md) — Cockcroft-Gault with adjusted weight.
- [BMI Calculator](https://tttkmbb.com/health/bmi.md) — Weight classification for the same height and weight.