# PaO2/FiO2 Ratio Calculator

> PaO2/FiO2 Ratio Calculator is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Computes the P/F ratio (arterial partial pressure of oxygen divided by fraction of inspired oxygen) rounded to one decimal place.

## Facts

- Endpoint: GET https://api.magentlab.com/api/calc/pf_ratio
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/pao2-fio2-ratio-calculator-37b007ff
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_7VQxIgByMj4pPxSpnVsNa

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability pao2-fio2-ratio-calculator-37b007ff
```

Example prompt: Calculate the P/F ratio for a patient with a PaO2 of 75 mmHg on an FiO2 of 0.40.

## When to prefer this

Use this endpoint when you need a fast, accurate arithmetic P/F ratio computation from a known PaO2 (mmHg) and FiO2 fraction for clinical decision support, charting, or automated workflows. Prefer this over manual calculation when embedding in agent pipelines, EHR integrations, or when consistency and rounding convention matter. Do not use if you need ARDS severity classification, the oxygenation index (OI), or the SpO2-based S/F ratio (use the sibling S/F endpoint for that).

## Known failure modes

- Missing required parameter pao2_mm_hg or fio2 returns an error
- FiO2 value outside 0.21–1.0 range may be rejected or produce clinically invalid result
- PaO2 value outside 20–700 mmHg range may be rejected
- Non-numeric input causes validation error
- Network timeout or API unavailability returns HTTP error

## How this service works

PaO2/FiO2 ratio as arterial PO2 in mm Hg divided by inspired oxygen as a fraction (0.21–1.0). Returns the ratio rounded to one decimal. Magent does not apply ARDS severity cutoffs, and this is not the oxygenation index (FiO2 × MAP × 100 / PaO2).

## Output

Returns a single numeric P/F ratio value (PaO2 divided by FiO2) rounded to one decimal place. Does not apply ARDS severity thresholds (Berlin Definition cutoffs of <100, <200, <300) or compute the oxygenation index (FiO2 × MAP × 100 / PaO2).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "headers": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    },
    "queryParams": {
     "type": "object",
     "required": [
      "pao2_mm_hg",
      "fio2"
     ],
     "properties": {
      "fio2": {
       "type": "number",
       "description": "Inspired oxygen as a fraction (0.21-1.0), not a percent. Required."
      },
      "pao2_mm_hg": {
       "type": "number",
       "description": "Arterial PO2 in mm Hg (20-700)."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "path": "/api/calc/pf_ratio",
  "count": 2,
  "items": [
   {
    "fio2": 0.21,
    "formula": "pf_ratio",
    "citation": {
     "id": "horovitz-1974",
     "doi": "10.1001/archsurg.1974.01350270079014",
     "title": "Pulmonary response to major injury",
     "source": "Arch Surg. 1974;108(3):349-355",
     "authors": "Horovitz JH, Carrico CJ, Shires GT"
    },
    "pf_ratio": 452.4,
    "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.",
    "pao2_mm_hg": 95,
    "formula_expression": "pf_ratio = pao2_mm_hg / fio2"
   },
   {
    "fio2": 0.21,
    "formula": "pf_ratio",
    "citation": {
     "id": "horovitz-1974",
     "doi": "10.1001/archsurg.1974.01350270079014",
     "title": "Pulmonary response to major injury",
     "source": "Arch Surg. 1974;108(3):349-355",
     "authors": "Horovitz JH, Carrico CJ, Shires GT"
    },
    "pf_ratio": 452.4,
    "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.",
    "pao2_mm_hg": 95,
    "formula_expression": "pf_ratio = pao2_mm_hg / fio2"
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/pao2-fio2-ratio-calculator-37b007ff/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.magentlab.com](https://www.zero.xyz/host/api.magentlab.com/llms.txt)