Duct Calculator, developed by LetsFab, is a free Android application designed for HVAC engineers and designers who work in the field of ventilation system design and installation. This app is a valuable tool for everyday design and construction work, making it easier to calculate duct size required with available CFM and FPM.

This app is capable of calculating both rectangular and round duct sizes in inches, making it a versatile tool for HVAC engineers. Additionally, Duct Calculator can also calculate air flow rate in CFM and air velocity in FPM. The app's user-friendly interface and accurate calculations make it a must-have tool for anyone in the HVAC industry.