Jun 14, 2016· 25,400 microns = 1 inch; So then what does mesh size mean? The way in which to figure out the mesh size of a paint filter is quite simple. If you took the time, all you have to do is count the number of openings in one inch of screen. The total number of openings becomes the mesh size. With that being said, a 30 mesh screen has 30 openings, 100 ...