Duct Calculator: HVAC Sizing

The digital ductulator — equal-friction duct sizing in your pocket, no cardboard slide rule. Enter airflow (CFM) and a friction rate, get an instant duct size: ROUND DUCT - Exact required diameter, plus the nearest standard size - Air velocity, flagged if it's above safe residential limits RECTANGULAR DUCT - Fix one side, get the matching size for your target equivalent diameter - Equivalent round diameter (Huebscher) for cross-checking against round runs BUILT ON REAL PHYSICS - Darcy–Weisbach + Colebrook friction factor — the same method behind the ASHRAE friction chart and professional ductulators — not a rough approximation. - Galvanized sheet metal, standard air. Supply (0.10 in wg/100ft) and return (0.08) defaults built in, or set your own friction rate. Free to download and try. Ductulator Pro unlocks unlimited calculations with a 7-day free trial, then renews yearly — cancel anytime in Settings. Terms: https://ductulator.vovaluka.com/terms Privacy: https://ductulator.vovaluka.com/privacy