Body size · LIVE

Boer estimated lean body mass

Boer LBM

Compute Boer 1984 sex-specific estimated lean body mass from height, weight, and sex.

LIVE $0.005 USDC GET /api/calc/ffm

Markdown: /docs/ffm.md · Canonical: https://magentlab.com/docs/ffm

Not a medical device. Not a diagnosis, dose, or listing recommendation.

What it computes

Compute Boer 1984 sex-specific estimated lean body mass from height, weight, and sex.

When to use

When an agent already has sex, height, and weight and must not invent kilograms, apply James or Hume formulas, or treat the result as a dosing weight or measured body composition.

When not to use

• Not a medical device. Not a dosing weight. Boer 1984 estimated lean body mass to normalize body fluid volumes; magent does not measure body composition.
• Boer 1984 sex-specific estimated lean body mass only. Does not apply James or Hume formulas.
• Height 100-220 cm and weight 20-300 kg are magent clamps, not published Boer input bands.
• Does not report fat mass. magent does not measure the patient.

Formula

male: LBM_kg = 0.407 × weight_kg + 0.267 × height_cm − 19.2; female: LBM_kg = 0.252 × weight_kg + 0.473 × height_cm − 48.3

Citation

Title

Estimated lean body mass as an index for normalization of body fluid volumes in humans

Authors

Boer P

Source

Am J Physiol. 1984;247(4 Pt 2):F632-F636

DOI

10.1152/ajprenal.1984.247.4.F632

Worked example

Also searched as

• estimated lean body mass
• Boer LBM
• Boer 1984 lean body mass
• fat-free mass Boer
• lean body mass height weight
• estimated LBM
• Boer FFM

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/ffm?sex=female&weight_kg=60&height_cm=163

Full URL: https://api.magentlab.com/api/calc/ffm?sex=female&weight_kg=60&height_cm=163

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/ffm?sex=female&weight_kg=60&height_cm=163"

Parameters

Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

POST /api/calc/ffm Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 PREVIEW

• 1 to 25 items. Each item uses the same keys as the GET query parameters.
• POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
• The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
• HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
• Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
• x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request (fixture)

{
  "items": [
    {
      "height_cm": "163",
      "sex": "female",
      "weight_kg": "60"
    },
    {
      "height_cm": "163",
      "sex": "female",
      "weight_kg": "60"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/ffm",
  "items": [
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Boer P",
        "doi": "10.1152/ajprenal.1984.247.4.F632",
        "id": "boer-1984",
        "pmid": "6496691",
        "source": "Am J Physiol. 1984;247(4 Pt 2):F632-F636",
        "title": "Estimated lean body mass as an index for normalization of body fluid volumes in humans"
      },
      "formula": "boer_lbm",
      "formula_expression": "male: LBM_kg = 0.407 × weight_kg + 0.267 × height_cm − 19.2; female: LBM_kg = 0.252 × weight_kg + 0.473 × height_cm − 48.3",
      "sex": "female",
      "weight_kg": 60.0,
      "height_cm": 163.0,
      "ffm_kg": 43.9,
      "lbm_kg": 43.9
    },
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Boer P",
        "doi": "10.1152/ajprenal.1984.247.4.F632",
        "id": "boer-1984",
        "pmid": "6496691",
        "source": "Am J Physiol. 1984;247(4 Pt 2):F632-F636",
        "title": "Estimated lean body mass as an index for normalization of body fluid volumes in humans"
      },
      "formula": "boer_lbm",
      "formula_expression": "male: LBM_kg = 0.407 × weight_kg + 0.267 × height_cm − 19.2; female: LBM_kg = 0.252 × weight_kg + 0.473 × height_cm − 48.3",
      "sex": "female",
      "weight_kg": 60.0,
      "height_cm": 163.0,
      "ffm_kg": 43.9,
      "lbm_kg": 43.9
    }
  ]
}

Response

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Boer P",
    "doi": "10.1152/ajprenal.1984.247.4.F632",
    "id": "boer-1984",
    "pmid": "6496691",
    "source": "Am J Physiol. 1984;247(4 Pt 2):F632-F636",
    "title": "Estimated lean body mass as an index for normalization of body fluid volumes in humans"
  },
  "formula": "boer_lbm",
  "formula_expression": "male: LBM_kg = 0.407 × weight_kg + 0.267 × height_cm − 19.2; female: LBM_kg = 0.252 × weight_kg + 0.473 × height_cm − 48.3",
  "sex": "female",
  "weight_kg": 60.0,
  "height_cm": 163.0,
  "ffm_kg": 43.9,
  "lbm_kg": 43.9
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

Related tools

• Devine IBW — Compute Devine ideal body weight and 0.4 adjusted body weight from height, sex, and actual weight.
• BMI — Compute Keys/Quetelet body-mass index from height and weight, plus a WHO adult band.

Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /docs/mcp.

Guarantees

• HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged. HTTP 402 never includes the tool JSON.
• exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
• HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
• Execution is timeout-bounded and concurrency-capped.
• Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.