Abstract: Aspects discussed herein relate to spirometers that can be used to measure lung function using a mobile device. A user can breathe into a mouthpiece that forces the user's breath through a spirometric encoding assembly. The spirometric encoding assembly can be coupled to a mobile device using a spirometric encoding adapter. The spirometric encoding assembly can generate one or more outputs based on the user's breath; this data can be measured using one or more sensors of the mobile device. The data captured by the mobile device can be processed to determine the flow rate and/or volume of the user's breath. The flow rate and volume can be used to determine a variety of characteristics of the user's health, lung capacity, and/or for diagnosing medical conditions.