{"uid":"cap_U1Nvsn_bDeRHj6oSWNKLH","slug":"magent-s-f-ratio-calculator-9ab4abab","name":"magent S/F Ratio Calculator","description":"SpO2/FiO2 (S/F) ratio as pulse-oximetry SpO2 percent divided by inspired oxygen as a fraction (0.21–1.0) (Rice 2007). Returns the ratio rounded to one decimal. Magent does not apply ARDS or Berlin bands. This is not the PaO2/FiO2 (P/F) ratio and not the ROX index.","url":"https://api.magentlab.com/api/calc/sf_ratio","method":"GET","headers":{},"bodySchema":{"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":["spo2_percent","fio2"],"properties":{"fio2":{"type":"number","description":"Inspired oxygen as a fraction (0.21-1.0), not a percent. Required."},"spo2_percent":{"type":"number","description":"Pulse-oximetry SpO2 as a percent (50-100)."}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object"}}}}},"responseSchema":{"type":"json","example":{"path":"/api/calc/sf_ratio","count":2,"items":[{"fio2":0.21,"formula":"sf_ratio","citation":{"id":"rice-2007","doi":"10.1378/chest.07-0617","title":"Comparison of the SpO2/FIO2 ratio and the PaO2/FIO2 ratio in patients with acute lung injury or ARDS","source":"Chest. 2007;132(2):410-417","authors":"Rice TW, Wheeler AP, Bernard GR, Hayden DL, Schoenfeld DA, Ware LB"},"sf_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.","spo2_percent":95,"formula_expression":"sf_ratio = spo2_percent / fio2"},{"fio2":0.21,"formula":"sf_ratio","citation":{"id":"rice-2007","doi":"10.1378/chest.07-0617","title":"Comparison of the SpO2/FIO2 ratio and the PaO2/FIO2 ratio in patients with acute lung injury or ARDS","source":"Chest. 2007;132(2):410-417","authors":"Rice TW, Wheeler AP, Bernard GR, Hayden DL, Schoenfeld DA, Ware LB"},"sf_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.","spo2_percent":95,"formula_expression":"sf_ratio = spo2_percent / fio2"}]}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_1xsmF4ca4z9izwDw6HW1y","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Calculates the SpO2/FiO2 (S/F) ratio by dividing pulse-oximetry SpO2 percentage by inspired oxygen fraction, returning the ratio rounded to one decimal place.","exampleAgentPrompt":"Calculate the S/F ratio for my patient who has an SpO2 of 94% and is on 40% inspired oxygen (FiO2 of 0.40).","exampleUseCases":[{"title":"ICU respiratory failure triage","prompt":"My ICU patient has an SpO2 of 88% and is on high-flow oxygen with FiO2 of 0.60 — what is their S/F ratio?"},{"title":"Non-invasive ARDS screening","prompt":"Can you compute the S/F ratio for a patient with SpO2 of 96% breathing room air (FiO2 0.21)? We want to assess oxygenation without an arterial blood gas."},{"title":"Serial oxygenation trending","prompt":"Track the S/F ratio for a patient whose SpO2 improved from 90% to 95% on FiO2 0.50 — calculate the new ratio so we can compare to the earlier value."}],"resultDescription":"Returns a single numeric S/F ratio (SpO2% ÷ FiO2 fraction) rounded to one decimal place. This is the Rice 2007 surrogate oxygenation index — not the P/F ratio and not the ROX index.","failureModes":["FiO2 outside 0.21–1.0 range returns validation error","SpO2 outside 50–100% range returns validation error","Missing required query parameters returns 400 error","Payment not provided or declined returns 402 error"],"whenToPreferThis":"Choose this endpoint when you need a fast, non-invasive oxygenation index and arterial blood gas (PaO2) is unavailable or impractical — i.e., when you have pulse-oximetry SpO2 but not a measured PaO2. Use the sibling PaO2/FiO2 endpoint instead when arterial blood gas values are available. Do not use this for ROX index (which incorporates respiratory rate) or for formal ARDS/Berlin criteria banding.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T01:08:12.917Z","isFirstParty":false}