Mesh (or mesh count) is the number of openings per linear inch, measured from the center of one wire to the center of the next.

To determine mesh size, count the number of openings between the center of one wire and the center of a parallel wire one inch away. For coarse mesh, this can usually be done with a ruler. For finer meshes, a mesh counter or optical comparator may be required for accuracy. Mesh count does not account for wire diameter, which also affects opening size and filtration.