Ductfolio: Duct Calculator

Size and check rigid round or rectangular HVAC ducts with clear calculations, dimensions and assumptions. Free calculations include one saved job, US and metric display units, and local backup. Pro unlocks comparisons, additional saved jobs, catalog editing, fit-to-space, pressure-loss assistance and PDF or CSV reports with one purchase. No subscription or account is required. Calculations and jobs stay on your device. Use a backup to keep a separate copy. Buying or restoring Pro requires internet access. Uses Darcy–Weisbach and Colebrook. Rectangular friction uses an equivalent round diameter; displayed velocity uses the actual area. For rigid round and rectangular ducts. No flexible-duct model, thermal loads, network balancing or code certification. Apply professional judgment and verify project requirements.