Particle Size Conversion Table | SigmaAldrich
Large sieve openings (1 in. to 1/4 in.) have been designated by a sieve "mesh" size that corresponds to the size of the opening in inches. Small sieve "mesh" sizes of 3 1/2 to 400 are designated by the number of openings per linear inch in the sieve. The following convention is used to characterize particle size by mesh designation: