The Duct Sizer App designed based on surveying the needs of engineers. This is a much faster and versatile equivalent of the duct sizing charts provided by top HVAC manufacturers. Get a range of suitable duct sizes by inputting either the maximum friction rate or maximum velocity. Duct sizing for both rectangular and circular ducts. Tap on the values for velocity or friction to switch between calculation methods. Users can change between I-P and S-I units by tapping the toggle switch at the top. The detailed sizing mode allows the Engineer to adjust the duct dimensions and air flow rates, while checking the resulting friction rate and velocity which update automatically. Detailed sizing mode is typically used to analyse existing duct systems, and was added upon the request of users' feedback. Calculations are based on standard air 0.075 lb/ft3 (1.2 kg/m3) in clean galvanized steel duct. Any feedback is welcome, and will be the basis for future updates.