Ductulator: HVAC Calculator

Size a duct from airflow in seconds — round, rectangular, or a whole trunk-and-branch run, right from the job site.

Stop guessing duct sizes.

Ductulator turns your airflow into the exact round or rectangular duct size you need — plus the friction rate, right from the job site.

Built for HVAC contractors and DIY installs alike: • Round and rectangular sizing from CFM and target velocity, fully free • Reverse mode — already have a duct size on hand? See what airflow it can carry (Pro) • Branch calculator — size a trunk and every branch run at once, with a warning if they don't add up (Pro) • Every duct material — Galvanized, Flex Duct, PVC, Fiberboard (Pro) • Save sizings by job and share a polished PDF with your crew (Pro)

No account, no ads, no guesswork — just the numbers you need before you cut metal.

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