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The smaller the abrasive particles, the finer the grit of the sandpaper and the smoother the finish it can produce. - Sandpaper grit graded by the number of abrasive particles per square inch of paper. The higher the number, the smaller the particles and the more particles per inch.
- In North America, the standard grading system for sandpaper comes from the Coated Abrasives Manufacturer's Institute (CAMI). In Europe, the Federation of European Producers Association (FEPA) has a separate system, and the grit number is preceded by a "P." A CAMI grit of 80 roughly corresponds to a FEPA grit of P100.
- For most woodworking applications, a grit of 150 to 180 is considered fine, and 280 extra fine. However, even more fine sandpaper, up to 600 grit, is also widely available. The CAMI scale goes to 2000, but grit finer than 600 is difficult to find.
- Sandpaper is also evaluated on the type of abrasive particles. Aluminum oxide grit is common for wood sanding because the grit tends to fragment into smaller sharp-edged pieces as it is used. Garnet is a natural abrasive used in very fine wood sanding grits.
- Most sanding work begins with a medium grade grit, such as 80 to 150, and progresses to finer (higher number) grits. Each successively finer grit removes the scratches of the previous grit, producing a smoother finish. Very fine grits are good for removing excess luster and superficial blemishes.
