A system for measuring an angle of repose includes an angle of repose device that holds a granular material, and a portable smart device having a camera and a processor. The angle of repose device is configured to open a slit to allow a first part of the granular material to remain in an upper chamber while a second part of the granular material moves freely, due to gravity, from the upper chamber to a lower chamber. The portable smart device uses the camera to take a digital image of the first part and the second part of the granular material and uses an app installed on the processor to calculate an internal angle of repose and an external angle of repose.