{"uid":"cap_d55_0SqYyKIdBpqIDI9c-","slug":"bicycle-wheel-size-calculator-50763d8c","name":"Bicycle Wheel Size Calculator","description":"Rolling circumference and diameter for common tyre sizes, or an estimate from rim bead diameter and tyre width in mm.","url":"https://bike-calc.x402tookit.com/wheel-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":[],"properties":{"tyre":{"type":"string","description":"A preset: 700x23c, 700x25c, 700x28c, 700x32c, 700x35c, 700x38c, 26x2.0"},"bsdMm":{"type":"number","description":"Rim bead seat diameter in mm (622 for 700c/29er, 584 for 650b/27.5, 559 for 26 inch MTB, 406 for 20 inch BMX)"},"tyreWidthMm":{"type":"number","description":"Tyre width in mm, with bsdMm, for an estimate"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"basis":{"type":["null","string"]},"source":{"type":["null","string"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"diameterMm":{"type":["null","number"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"diameterInches":{"type":["null","number"]},"circumferenceMm":{"type":["null","number"]},"revolutionsPerKm":{"type":["null","number"]},"metersPerRevolution":{"type":["null","number"]}}}}}}},"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_BMb58ZlEJjlRFmWA3WUOI","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":"Returns rolling circumference, diameter, and revolutions per km for a given tyre size, either from a preset tyre label or from rim bead seat diameter and tyre width.","exampleAgentPrompt":"What's the rolling circumference and diameter of a 700x28c tyre in millimetres, and how many revolutions would it make per kilometre?","exampleUseCases":[{"title":"GPS cycling computer wheel calibration","prompt":"I need to calibrate my cycling computer — what's the rolling circumference in mm of a 700x25c road tyre?"},{"title":"MTB wheel geometry for gearing calculations","prompt":"Can you give me the wheel diameter and circumference for a 26-inch MTB tyre that's 50mm wide, using a 559mm bead seat diameter?"},{"title":"Speed estimation for custom drivetrain build","prompt":"I'm building a 650b gravel bike with 584mm BSD rims and 47mm tyres — what's the circumference and revolutions per km so I can plan my gear ratios?"}],"resultDescription":"Returns the wheel's outer diameter in mm and inches, rolling circumference in mm, meters per revolution, and revolutions per kilometre. Also includes the basis of the calculation (preset lookup or estimate), an optional disclaimer about estimated values, and metadata such as timestamp and source.","failureModes":["Missing both 'tyre' preset and 'bsdMm'/'tyreWidthMm' parameters — endpoint cannot compute without at least one valid input","Unrecognised tyre preset string — no matching entry for the given label","Partial custom inputs — providing bsdMm without tyreWidthMm or vice versa may return a degraded or null result","Values outside plausible ranges (e.g. bsdMm of 0 or extremely large width) may produce nonsensical estimates"],"whenToPreferThis":"Use this endpoint when you need accurate wheel circumference or diameter figures — for calibrating GPS cycling computers, computing gear development distances, or feeding into cadence/speed calculations. It covers both common ISO tyre presets and custom rim+width combinations, making it more flexible than a static lookup table. Pair with the sibling gear-ratio endpoint when building complete drivetrain calculators.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-29T13:11:19.677Z","isFirstParty":false,"canonicalSlug":"bicycle-wheel-size-calculator-50763d8c"}