What the grit number means
Sandpaper is graded by the size of its abrasive particles. The grit number refers roughly to how many openings per inch a screen would need for the particles to pass through, so a higher number means smaller particles and a finer scratch. A 60-grit sheet is coarse and cuts quickly. A 220-grit sheet is fine and leaves a smooth surface with little cutting power.
There are different grading systems. Many sheets in North America use the CAMI scale, while others use the FEPA “P” scale, which you will see as a P before the number. The two agree at coarse and medium sizes only roughly and diverge more in finer grits. When mixing brands or following instructions, check the label and stay with one scale where possible.
Rough ranges
These ranges are typical for woodworking, and they vary by source and by project:
| Range | Typical grits | Common use |
|---|---|---|
| Coarse | 40 to 60 | Heavy removal, stripping old finish, leveling |
| Medium | 80 to 120 | Removing marks from coarse work, general shaping |
| Fine | 150 to 220 | Final surface prep before finish |
| Very fine | 320 and above | Between coats, polishing finishes |
For bare wood, many people stop around 180 or 220 before stain or a clear finish. Going much finer can burnish the surface and make some stains or finishes absorb unevenly, which matters for products meant to soak in.
The progression from coarse to fine
Each grit removes the scratches left by the previous one. If you jump from 60 straight to 220, the fine paper will not remove the deeper scratches in a reasonable time, and they often become visible after you apply stain. A common approach is to move up in steps of one or two stages, such as 80, 120, 180, then 220.
Some practical points:
- Start with the finest grit that will do the job. If the surface only needs light smoothing, you may not need a coarse grit at all.
- Spend enough time at each grit to remove the previous pattern. Wiping the surface with a damp cloth or mineral spirits (following product directions) can show remaining scratches.
- Sand with the grain at the final stages, since cross-grain scratches are most visible on wood.
- Clean off dust between grits so loose coarse particles do not scratch the surface.
Common abrasive materials
The material that makes up the grains affects how long the paper lasts and what it suits.
- Aluminum oxide: a durable, widely used abrasive for wood, metal and painted surfaces. It is a good general choice for both hand and machine use.
- Silicon carbide: very sharp but more brittle. It is common in wet-or-dry paper used on finishes, metal, plastics and between coats.
- Garnet: a natural abrasive that gives a fine finish on bare wood but wears down faster. It is used mostly for hand sanding.
- Ceramic alumina: an engineered abrasive designed for long life under heavy pressure, usually sold for machine use and often costing more.
- Zirconia alumina: tough and common on belts and discs for aggressive removal.
There are many other specialty grains. The details of matching these to materials and backings belong to the question of abrasive types.
Open coat and closed coat
Sandpaper can have the grains packed tightly (closed coat) or spaced apart (open coat). Open coat leaves gaps that help resist clogging on soft materials like paint, resinous woods and sticky finishes. Closed coat cuts more material per pass but clogs more readily. If your paper clogs repeatedly, try an open coat product, lighter pressure or a cleaning stick for belts and discs.
Reading the label
Packaging usually shows the grit, abrasive type, size, and whether it is intended for wood, metal, drywall or wet use. Newer products may also have a descriptive grade such as coarse, medium or fine. The backing type, such as paper, cloth or film, also affects flexibility and durability. If a pack lacks clear grit information, it may be best to choose another.
When to replace paper
Worn sandpaper stops cutting and starts to polish and heat the surface. It may also leave burn marks on wood or glaze finishes. Replace paper when it clogs, tears, loses cutting speed or feels smooth under your fingers. Fresh paper is cheaper than a ruined project. Dust from sanding paint on older homes may contain lead, so research safe practices and wear appropriate protection before sanding it.
A short buying approach
For a small home toolkit, many people buy a range of sheets and discs in a few grits, such as 80, 120, 180 and 220, plus a very fine grade for finishes. Match disc sizes to your sander. Hook-and-loop discs generally swap quickly, and you can use any sheet with a block or by hand. Buy more of the grits you use most often rather than large assortments you may never finish.
Always wear eye protection and a dust mask suited to the material, and unplug a sander before changing discs.