# Relative fat mass (RFM) RFM Status: LIVE Price: $0.005 USDC `GET /api/calc/rfm` HTML: https://magentlab.com/docs/rfm Markdown: https://magentlab.com/docs/rfm.md Not a medical device. Not a diagnosis, dose, or listing recommendation. ## What it computes Compute Woolcott 2018 relative fat mass (RFM) from height, waist circumference, and sex as an estimator of whole-body fat percentage. ## When to use When an agent needs published RFM from height, waist, and sex and must not invent a body-fat percentage or apply later obesity cutoffs that are not in Woolcott 2018. ## When not to use - Not a medical device and not a body-fat diagnosis. magent does not measure the patient. - Woolcott 2018 is the RFM estimate only. magent does not apply later obesity cutoffs that are not in that paper. ## Formula ``` RFM = 64 - (20 * (height_m / waist_m)) + (12 * sex); sex = 0 male, 1 female ``` ## Citation [Relative fat mass (RFM) as a new estimator of whole-body fat percentage ─ A cross-sectional study in American adult individuals](https://doi.org/10.1038/s41598-018-29362-1) Woolcott OO, Bergman RN Sci Rep. 2018;8:10980 DOI: [10.1038/s41598-018-29362-1](https://doi.org/10.1038/s41598-018-29362-1) ## Worked example ### 180 cm, waist 90 cm, male Given: `height_cm=180, sex=male, waist_cm=90` 1. height_m = 180 / 100 = 1.8; waist_m = 90 / 100 = 0.9; sex = 0 (male) 2. RFM = 64 - (20 * (1.8 / 0.9)) + (12 * 0) = 64 - 40 = 24.0 ## Also searched as - relative fat mass - RFM - Woolcott RFM - height-to-waist fat mass - Woolcott Bergman RFM - RFM body fat percentage - whole-body fat percentage estimator ## Parameters - `height_cm` (number, optional): Height in centimeters. Provide height_cm or height_in. - `height_in` (number, optional): Height in inches. Converted as cm = in * 2.54. - `waist_cm` (number, required): Waist circumference in centimeters (40-200). Converted to meters for RFM. - `sex` (string, required): Sex used by Woolcott 2018 (0 male, 1 female in the RFM equation). ## 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. Method: `POST /api/calc/rfm` Max items: 25 Price: unit_amount + extra_item_amount * (n - 1) (unit 5000 atomic, extra 2000 atomic) Status: 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: ```json { "items": [ { "height_cm": "180", "sex": "male", "waist_cm": "90" }, { "height_cm": "180", "sex": "male", "waist_cm": "90" } ] } ``` Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/rfm Example 200: ```json { "count": 2, "path": "/api/calc/rfm", "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": "Woolcott OO, Bergman RN", "doi": "10.1038/s41598-018-29362-1", "id": "woolcott-2018", "pmid": "30030479", "source": "Sci Rep. 2018;8:10980", "title": "Relative fat mass (RFM) as a new estimator of whole-body fat percentage ─ A cross-sectional study in American adult individuals" }, "formula": "rfm", "formula_expression": "RFM = 64 - (20 * (height_m / waist_m)) + (12 * sex); sex = 0 male, 1 female", "sex": "male", "height_cm": 180.0, "waist_cm": 90.0, "rfm": 24.0 }, { "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": "Woolcott OO, Bergman RN", "doi": "10.1038/s41598-018-29362-1", "id": "woolcott-2018", "pmid": "30030479", "source": "Sci Rep. 2018;8:10980", "title": "Relative fat mass (RFM) as a new estimator of whole-body fat percentage ─ A cross-sectional study in American adult individuals" }, "formula": "rfm", "formula_expression": "RFM = 64 - (20 * (height_m / waist_m)) + (12 * sex); sex = 0 male, 1 female", "sex": "male", "height_cm": 180.0, "waist_cm": 90.0, "rfm": 24.0 } ] } ``` ## Response fields - `formula` (string): rfm - `formula_expression` (string): Exact expression used - `sex` (string): female or male - `height_cm` (number): Normalized height in cm - `waist_cm` (number): Waist circumference in cm - `rfm` (number): Relative fat mass, 1 decimal. Not a body-fat diagnosis. - `citation` (object): Woolcott 2018 citation - `disclaimer` (string): Not-a-device notice ## Example JSON Frozen fixture. Not a live lookup. ```json { "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": "Woolcott OO, Bergman RN", "doi": "10.1038/s41598-018-29362-1", "id": "woolcott-2018", "pmid": "30030479", "source": "Sci Rep. 2018;8:10980", "title": "Relative fat mass (RFM) as a new estimator of whole-body fat percentage ─ A cross-sectional study in American adult individuals" }, "formula": "rfm", "formula_expression": "RFM = 64 - (20 * (height_m / waist_m)) + (12 * sex); sex = 0 male, 1 female", "sex": "male", "height_cm": 180.0, "waist_cm": 90.0, "rfm": 24.0 } ``` ## Errors - HTTP 400 `invalid_height`: height_cm (50-250) or height_in (20-98) is required Returned before settlement; you are not charged. - HTTP 400 `invalid_sex`: sex must be female or male Returned before settlement; you are not charged. - HTTP 400 `invalid_waist_range`: waist_cm must be a number from 40 to 200. Returned before settlement; you are not charged. - HTTP 400 `invalid_items`: POST body must be a JSON object with only an items array Returned before settlement; you are not charged. - HTTP 400 `invalid_item_count`: items must be an array of 1 to 25 objects Returned before settlement; you are not charged. - HTTP 400 `invalid_item`: each items entry must be a JSON object Returned before settlement; you are not charged. Shared HTTP 402 and 503: https://magentlab.com/docs/payments ## Related tools - [BMI](https://magentlab.com/docs/bmi) — Compute Keys/Quetelet body-mass index from height and weight, plus a WHO adult band. - [BRI](https://magentlab.com/docs/bri) — Compute Thomas 2013 body roundness index from height and waist by modeling the body as an ellipse. ## 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. - GET the tool with Accept: application/json (do not send Accept: text/html unless you want the human paywall). - HTTP 402 means you have not paid. Decode the base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote. - Sign accepts[0] (exact, EIP-3009) with validBefore = now + maxTimeoutSeconds (600 seconds), or accepts[1] (batch-settlement deposit/voucher) on product GET. Ping and POST {items} stay exact. Magent retries transient facilitator 429/5xx before answering. - Retry the same URL with PAYMENT-SIGNATURE (base64 JSON of accepted and payload). Magent attaches canonical extensions.bazaar on CDP verify/settle; echoing 402 bazaar is optional. - Success is HTTP 200 JSON plus PAYMENT-RESPONSE. exact settles before the tool. batch-settlement verifies (and deposit-settles) before the tool and commits the charge after HTTP 2xx. HTTP 503: retry the same PAYMENT-SIGNATURE. Mint a new exact nonce only after a new HTTP 402. - offered `exact` on eip155:8453: Fixed-price USDC on Base. The buyer authorizes the advertised amount (EIP-3009). magent settles before the tool runs (paymentFlow upfront). extra.assetTransferMethod=eip3009 extra.paymentFlow=upfront. - offered `batch-settlement` on eip155:8453: Payment-channel vouchers claimed later in batches. Exact stays accepts[0]. Same-path POST {items} is still exact. extra.assetTransferMethod=eip3009 extra.paymentFlow=authorization. - not offered `upto`: Not offered. Usage-based: buyer authorizes a ceiling, seller settles the actual amount after work. Reserved for a future metered tool. Not for current calculators or code search. Same-path POST {items} is still scheme exact: one EIP-3009 authorization for GET unit plus $0.002 per extra item. That is not x402 batch-settlement (payment channels / vouchers). Shared HTTP 402 and 503 table: https://magentlab.com/docs/payments Stdio MCP (one process per host): https://magentlab.com/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.