Studor’s Airflow Calculator is a free app for IOS devices, which provides an airflow calculations based on based on European Standard EN12056-2:2000 - Gravity Drainage System inside buildings. The user can select System I or System II, select an appropriate Frequency Factor, enter the number of devices of each type and the number of floors of the building. The resulting calculations include the total number of Discharge Units and airflow requirements. These can be cross-referenced with the tables from the standard to determine the diameter of pipe needed based on the loading capacity. A calculation of the total number of Studor AAVs required to vent the drainage system is also provided.