Nancy LT Hamilton
This chart is based on 3M’s PDF and the ANSI chart for US standards: American National Standards Institute (see the bottom of the page). Dieter Schmid Fine Tools has a conversion chart for other countries: the Federation of European Producers of Abrasives standards (FEPA P – for sandpapers) (FEPA F – for sharpening stones and wheels) and the JIS, Japanese Industrial Standard – English version.
The International Gem Society has great information on Microns, Grits, and Mesh, if you’d like further research. They also explain what they all mean and have conversion charts!
Okay, here we go!