CAMI · FEPA · microns
Know your grit.
Type a grit number and get the particle size, the equivalent in the other numbering system, and what that paper is actually for.
CAMI is the US scale (80, 220). FEPA is the European scale, written with a P (P80, P220). They are not the same numbers.
The chart, at a glance
Six grits cover almost everything a home workshop does. The rest exist for finishing and polishing, where the differences get small enough that only the micron figure is useful.
| Grit | FEPA | Microns | Used for |
|---|---|---|---|
| 40 | P40 | 425 | Strip |
| 80 | P80 | 190 | Shape |
| 120 | P120 | 125 | Prep |
| 180 | P180 | 82 | Finish |
| 220 | P220 | 68 | Finish |
| 400 | P400 | 35 | Polish |
What grit do I need?
Pick the job and get the sequence, not just a single number — the order matters more than any one grit.
Why the number on the paper is not enough
Three things decide what a sheet of sandpaper does: the grit, the backing, and whether it is open or closed coat. The grit number only tells you the particle size. A 120-grit open-coat paper on a soft backing cuts differently from a 120-grit closed-coat paper on a hard one, even though both say 120.
Open coat means the abrasive covers 40 to 70 percent of the surface, leaving gaps that let dust escape. It resists clogging on soft woods and paint. Closed coat covers the whole sheet and cuts faster, but it loads up quickly on resinous timber.
Then there is the numbering. US paper uses CAMI numbers, European paper uses FEPA with a P prefix, and they do not line up exactly. A CAMI 220 and a FEPA P220 are close, but P220 is slightly finer. If you order paper from abroad at the same number, expect a slightly different scratch. The micron figures in the chart are the only numbers that mean the same thing everywhere.
The one rule that matters
Each grit only removes the scratches left by the previous one. That is why jumping from 80 straight to 220 wastes both sheets: the 220 polishes the tops of the 80-grit grooves instead of removing them, and the scratches reappear the moment finish goes on.
Never skip more than one step in the sequence. On bare wood the standard run is 80, 120, 180, 220. Stop at 220 — going finer burnishes the surface so stain cannot soak in evenly. On finish, work up through 320, 400 and beyond, and wet-sand the fine grits so the paper does not clog.
Questions people ask
What does the grit number on sandpaper mean?
It is a count of abrasive particles per square inch. A higher number means smaller particles and a finer scratch — 40 grit is coarse enough to strip paint, 220 is the last grit before most finishes, and 1000 grit is polishing.
Is 220 or 320 grit finer?
320. The bigger the number, the finer the paper. 220 leaves a scratch you can feel with a fingernail; 320 leaves one you can only see under raking light.
What is the difference between CAMI and FEPA grit numbers?
CAMI is the American scale, written as a plain number (80, 120, 220). FEPA is the European scale, written with a P (P80, P120, P220). They are close but not identical — P220 is slightly finer than CAMI 220 — which is why sandpaper bought in the US and Europe can behave differently at the same number.
What grit should I use on bare wood?
Start at 80 if the surface is rough, then work 120, 180 and stop at 220. Going finer than 220 on bare wood burnishes the surface and stops stain absorbing evenly.
Can I skip a grit when sanding?
Not more than one step. Each grit only erases the scratches of the one before it; jump from 80 to 220 and the coarse scratches are still there, just polished over. They show up the moment finish goes on.
What grit is 400 sandpaper in microns?
About 35 microns average particle size. CAMI 400 sits close to FEPA P400 and is used for wet-sanding between clear coats.