{"uid":"cap_3u4G5gGxh4wkFYPnxaz88","slug":"automotive-gear-rpm-calculator-e0d1c608","name":"Automotive Gear RPM Calculator","description":"Engine RPM at a road speed (or speed at an RPM) from tire size, axle ratio and transmission gear ratios, with a table by gear.","url":"https://automotive-calc.x402tookit.com/gear-rpm?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":["tire","axleRatio"],"properties":{"rpm":{"type":"number","description":"Engine RPM, to find the speed instead"},"tire":{"type":"string","description":"Tire size like 265/70R17, or a diameter in inches like 28"},"gears":{"type":"string","description":"Gear ratios as gear:ratio separated by semicolons, for example '1:3.59; 2:2.19; 3:1.41; 4:1.00; 5:0.83'"},"speed":{"type":"number","description":"Road speed (give this, or rpm)"},"axleRatio":{"type":"number","description":"Final drive (axle) ratio, 1 to 8, for example 3.73"},"gearRatio":{"type":"number","description":"One transmission gear ratio (default 1, direct drive); use gears for several"},"speedUnit":{"type":"string","description":"mph (default) or kmh"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"gears":{"type":["array","null"],"items":{"type":"object","properties":{"rpm":{"type":["null","number"]},"gear":{"type":["null","string"]},"gearRatio":{"type":["null","number"]},"overallRatio":{"type":["null","number"]}}}},"speed":{"type":["null","number"]},"source":{"type":["null","string"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"speedMph":{"type":["null","number"]},"axleRatio":{"type":["null","number"]},"speedUnit":{"type":["null","string"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"tireDiameterInches":{"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_RsqFIa8EMV38Sh8j_1Tm2","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":"Calculates engine RPM at a given road speed (or speed at a given RPM) based on tire size, axle ratio, and transmission gear ratios, returning a per-gear table.","exampleAgentPrompt":"What RPM will my engine be at 70 mph in each gear? My truck has 265/70R17 tires, a 3.73 axle ratio, and gear ratios of 1:3.59, 2:2.19, 3:1.41, 4:1.00, 5:0.83.","exampleUseCases":[{"title":"Highway cruise RPM after axle swap","prompt":"I just swapped to 4.10 gears on my Jeep with 35-inch tires and a 6-speed transmission with ratios 1:4.46, 2:2.61, 3:1.72, 4:1.25, 5:1.00, 6:0.84 — what RPM will I be cruising at in 6th gear at 65 mph?"},{"title":"Speed at redline for each gear","prompt":"My motorcycle engine redlines at 10500 RPM, it has a 120/70R17 front tire effectively 23.5 inches diameter, a final drive ratio of 2.88, and gears 1:2.46, 2:1.75, 3:1.33, 4:1.07, 5:0.89, 6:0.79 — what speed in mph will I be doing at redline in each gear?"},{"title":"Tire size effect on cruising RPM","prompt":"I'm upsizing my tires from 225/65R17 to 265/70R17 on a truck with a 3.55 axle ratio and a single overdrive gear ratio of 0.70 — what will my highway RPM be at 75 mph before and after the tire change?"}],"resultDescription":"Returns a JSON object containing the calculated road speed or engine RPM, a per-gear table showing each gear name, gear ratio, overall ratio, and RPM at the given speed (or speed at the given RPM), plus the tire diameter in inches, axle ratio used, speed unit, a summary string, and any disclaimer or degraded-data flags.","failureModes":["Missing required tire or axleRatio parameters returns a validation error","Malformed tire size string (e.g. not in NNN/NNRNN format or plain inches) may cause a parse error","Neither speed nor rpm provided causes ambiguous or error response","Axle ratio outside 1–8 range may produce invalid results","Gear ratio string not formatted as 'gear:ratio; gear:ratio' may fail to parse"],"whenToPreferThis":"Use this endpoint when you need precise drivetrain RPM-to-speed or speed-to-RPM calculations based on actual tire size, axle ratio, and multi-gear transmission ratios. Ideal for automotive enthusiasts, mechanics, or fleet managers evaluating gear swaps, tire upsizing, or engine operating ranges across all gears simultaneously.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-29T13:13:47.381Z","isFirstParty":false,"canonicalSlug":"automotive-gear-rpm-calculator-e0d1c608"}