{"uid":"cap_8o0jGXFQLtQuSnS1WGveB","slug":"hvac-duct-equivalent-round-diameter-calculator-d50e3266","name":"HVAC Duct Equivalent Round Diameter Calculator","description":"Equivalent round diameter of a rectangular duct (same friction), or the second side that matches a round duct.","url":"https://hvac-calc.x402tookit.com/duct-equivalent?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":["sideA"],"properties":{"sideA":{"type":"number","description":"One side of the rectangular duct (inches or any unit)"},"sideB":{"type":"number","description":"Other side, same unit; send this or roundDiameter"},"roundDiameter":{"type":"number","description":"Round duct diameter to find the matching second side"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"sideA":{"type":["null","number"]},"sideB":{"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"]},"roundArea":{"type":["null","number"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"aspectRatio":{"type":["null","number"]},"rectangularArea":{"type":["null","number"]},"equivalentRoundDiameter":{"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_yI5n1O8sq4e7XJ6-vVBur","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 the equivalent round duct diameter for a rectangular duct (same friction loss), or finds the missing rectangular side that matches a given round duct diameter.","exampleAgentPrompt":"What's the equivalent round duct diameter for a rectangular duct that's 16 inches wide and 10 inches tall? I need to find the round size with the same friction loss.","exampleUseCases":[{"title":"Rectangular to round duct conversion","prompt":"I have a 24 by 12 inch rectangular duct and I need to know what diameter round duct would give me the same friction loss — can you calculate the equivalent round diameter?"},{"title":"Find matching rectangular duct side","prompt":"I've got a 14-inch round duct that I need to replace with a rectangular duct, and one side has to be 10 inches. What should the other side be to match the same friction?"},{"title":"Duct sizing for HVAC retrofit","prompt":"We're replacing flex duct with rigid rectangular duct in a retrofit. The old round duct was 12 inches — if I use a 16-inch wide rectangular duct, what height do I need to match it?"}],"resultDescription":"Returns the equivalent round diameter for the given rectangular duct dimensions (or the missing rectangular side), along with aspect ratio, rectangular cross-sectional area, round cross-sectional area, and a text summary. May include a disclaimer and degraded/error flags.","failureModes":["Missing required sideA parameter returns an error","If neither sideB nor roundDiameter is provided, the calculation cannot resolve both unknowns","Non-numeric or negative input values may return validation errors","Service may return a degraded flag if partial results are available","Network or payment-related failures (402 payment required if USDC not provided)"],"whenToPreferThis":"Use this endpoint when you need to size round or rectangular HVAC ducts to have equivalent friction loss — particularly when retrofitting between duct shapes, selecting fittings, or performing duct layout design. It is purpose-built for the HVAC equivalent round diameter formula, making it more reliable and accurate than a general-purpose calculator or LLM arithmetic.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-29T13:14:27.279Z","isFirstParty":false,"canonicalSlug":"hvac-duct-equivalent-round-diameter-calculator-d50e3266"}