The international standards for grits

In the international chaos of different grits: Mesch, Micron, JIS, FEPA

This comparison table is somewhat inaccurate. But maybe it can at least give a few clues. Unfortunately, there are no formulas for the conversion, so you always seem to have to rely on tables. And unfortunately, the abrasive media often do not even mention the standard according to which the grit is specified.

Mesh is the number of meshes for sieving abrasive grains per square inch (i.e., an American standard).

Micron is a thousandth of a millimeter and here a measure of the size of the abrasive grains.

JIS means the grit size measured in the Japanese standard. So, at least for the Japanese stones, we can assume that they are described according to this standard.

FEPA-F applies to grinding stones, FEPA-P for abrasive paper. Both are European standards.

DMT is a large manufacturer of diamond "stones".

MeshMicronJISFEPA-FFEPA-PName
120125120120120DMT: extra-extra-coarse
22060240220240DMT: extra-coarse
32544330290280DMT: coarse
60022600400700DMT: fine
1200912006001500DMT: extra-fine
4000620008002200unknown
80003400012005000DMT: extra-extra-fine

A few sources on this inexhaustible topic: