Abrasive Grit to Micron Converter
Convert abrasive and grinding grit sizes to micron measurements.
Covers ANSI (CAMI), FEPA (P-grade), and JIS standards for grinding wheels, abrasive belts, and blasting media.
Select an abrasive grit size — see the micron equivalent across standards.
Abrasive grit sizes indicate the coarseness of grinding, cutting, and polishing materials. The grit number corresponds to the number of openings per linear inch in the screen used to sort abrasive particles. A higher grit number means smaller particles and a finer finish.
Three major standards exist worldwide:
ANSI/CAMI (American National Standards Institute / Coated Abrasive Manufacturers Institute) is the primary standard used in North America. It applies to coated abrasives like sandpaper, sanding belts, and abrasive discs. The grit numbers range from about 12 (very coarse) up to 1200 (ultra fine).
FEPA (P-grade) is the European standard maintained by the Federation of European Producers of Abrasives. FEPA grits are prefixed with “P” (e.g., P120, P400). At lower grits, FEPA and ANSI numbers are similar, but they diverge significantly above grit 220. For example, ANSI 220 is about 68 microns, while FEPA P220 is about 65 microns. The difference grows larger at finer grits.
JIS (Japanese Industrial Standards) is used primarily in Asia. JIS grits tend to run slightly finer than ANSI equivalents at the same number. JIS is especially common for waterstone sharpening grits used in knife and tool sharpening.
Approximate grit to micron conversion formula: Microns = 25,400 / Grit Number. This formula gives a rough estimate. Actual particle sizes are defined by each standard and measured by laboratory screening or laser diffraction. The formula is most accurate in the mid-range (80-400 grit) and less reliable at the extremes.
Practical guidelines for choosing abrasive grit:
- 24-60 grit: Heavy stock removal, rust stripping, grinding welds
- 80-120 grit: Shaping, leveling surfaces, removing old finishes
- 150-220 grit: Preparing surfaces for primer or sealant
- 320-600 grit: Between coats of finish, light smoothing
- 800-2000 grit: Final polishing, automotive clear coat, mirror finishes
The relationship between grit and surface roughness (Ra) is also important in machining. A 120-grit abrasive typically produces a surface roughness of about 1.0 to 1.6 micrometers Ra, while a 600-grit abrasive can achieve 0.1 to 0.2 micrometers Ra.