{"uid":"cap_7tz9hl2CEOYR9Gd_M4WI8","slug":"bicycle-frame-size-calculator-19ca4455","name":"Bicycle Frame Size Calculator","description":"Rough bike frame size (seat tube cm and S/M/L) from inseam by bike type, with a height-based letter size cross-check.","url":"https://bike-calc.x402tookit.com/frame-size?utm_source=zero.xyz","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"],"type":"string"},"queryParams":{"type":"object","required":["inseam"],"properties":{"unit":{"type":"string","description":"cm (default) or in"},"inseam":{"type":"number","description":"Inseam in cm (or inches with unit=in)"},"bikeType":{"type":"string","description":"road, road-compact, gravel, mountain, hybrid, city (default road)"},"heightCm":{"type":"number","description":"Body height in cm, for the S/M/L cross-check"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"factor":{"type":["null","number"]},"source":{"type":["null","string"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"bikeType":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"heightCm":{"type":["null","number"]},"inseamCm":{"type":["null","number"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"seatTubeCm":{"type":["null","number"]},"nearestEvenCm":{"type":["null","number"]},"seatTubeInches":{"type":["null","number"]},"adjacentSizesCm":{"type":["array","null"],"items":{"type":"number"}},"letterSizeFromHeight":{"type":["null","string"]},"mountainBikeInchesIfApplicable":{}}}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","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":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_X-QbvVx_Rg28Ya6cuvtL8","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Estimates bicycle frame size (seat tube in cm and S/M/L letter size) from inseam measurement and bike type, with an optional height-based letter size cross-check.","exampleAgentPrompt":"I have an inseam of 81 cm and I'm shopping for a road bike — what frame size should I be looking at, and what's my S/M/L size if I also give you my height of 178 cm?","exampleUseCases":[{"title":"Road bike purchase sizing","prompt":"I'm 175 cm tall with a 30-inch inseam and I want to buy a road bike — can you tell me what frame size in cm I should look for and whether that's a medium?"},{"title":"Mountain bike fit for a beginner","prompt":"My inseam is 76 cm and I'm buying my first mountain bike. What frame size do I need in both cm and the S/M/L sizing?"},{"title":"Gravel bike sizing cross-check","prompt":"I'm 183 cm tall with an 84 cm inseam and I'm looking at gravel bikes — what seat tube length should I target, and does my height-based letter size match?"}],"resultDescription":"Returns the estimated seat tube length in cm (and inches), the nearest even cm size, adjacent sizes for comparison, the S/M/L letter size derived from inseam, an optional letter size cross-check from body height, the bike type used, and a disclaimer about the estimates being a starting point rather than a definitive fit.","failureModes":["Missing required inseam parameter returns a 400 error","Inseam value outside plausible human range may return degraded or null results","Invalid bikeType string falls back to default road calculation","Providing height without inseam still requires inseam as it is required","Unit mismatch (e.g. passing inches without unit=in) yields incorrect frame size"],"whenToPreferThis":"Use this endpoint when you need a quick, formula-based starting frame size estimate from inseam and bike type, especially when the user does not yet have a specific bike in mind and wants a cm seat tube length plus letter size. It covers road, road-compact, gravel, mountain, hybrid, and city bike types. Prefer this over a full bike fitting service when no professional fit data is available and a rough estimate is sufficient.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-30T00:34:48.967Z","isFirstParty":false,"canonicalSlug":"bicycle-frame-size-calculator-19ca4455"}