Consequently, the higher the “grit” number results in a finer abrasive and will produce a smoother surface finish. The lower the “grit” number results in a coarser abrasive that will remove material much faster.

If the grit number is preceded by the letter "P", such as P2000, this indicates FEPA 2000 grit, as opposed to ANSI. Most sandpaper today is manufactured according to the international FEPA standard, while ANSI is the traditional American standard.

Sanding methods:

Knowing your intention for the finished product before starting will make it easier to properly prepare the item being treated. The common approach to sanding is to begin with a lower grit paper, or coarser paper, and increase the fineness of the sandpaper until desired results are achieved.

Metal:

Begin with loosening and scraping any loose paint or rust with a metal-toothed brush or coarse steel wool. Starting with a coarse grade of sandpaper move regularly over surface. Continue in this manner with increasingly finer grades of sandpaper until sufficient level of desired smoothness.

Wood:

For best results, always sand in the direction of the wood grain. Typically 100 grit or 120 grit is recommended to remove or smooth out any paint or dirt on the surface being addressed. A final pass with 220 grit to 360 grit will create a sufficiently smooth surface for painting, staining and varnishing.

Plaster:

For plaster surfaces such as drywall, 120 grit to 180 grit should be sufficient for most surfaces. Plaster quickly wears away, and the surface of fine sandpaper can easily become filled with plaster dust, rendering fine sandpaper ineffective.