Simply film the object you want to calculate the RPM of in slow motion. Lower framerates like 30 and 60 works for slower spinning objects but if it's spinning really fast I would suggest at least 120 FPS and ideally 960 FPS or over.
Currently the only phone capable of 960 FPS is the Xperia XZ Premium but other high-end phones can shoot in 240 FPS which is good enough for most purposes.
Bug fixes
9Apps 4.9
