P320 sandpaper
46.2 µm grain
P320 (FEPA) · about 280 grit (CAMI) · 0.046 mm average particle
What P320 is for
De-nibbing between coats. A P320 packet and a 320 packet are not the same paper: P320 is nearer CAMI 280.
The two scales
| FEPA (European) | P320 |
| CAMI (American) | about 280 |
| Average grain | 46.2 µm |
| Scales agree here? | No — P320 is about 14% coarser than a CAMI 320 |
A packet marked 320 in the United States is finer than one marked P320 in Europe. The P prefix is the tell, and it is easy to miss on a label — which is why a finishing schedule copied from an American source and followed with European paper comes out coarser than intended at every step.
Nearby grits
| FEPA | CAMI | Grain | Typically |
|---|---|---|---|
| P180 | 180 | 82 µm | The last grit where P and CAMI still mean nearly the same thing |
| P220 | 220 | 68 µm | The last grit most woodwork needs before paint or stain, and the point where the two scales still agree closely enough to substitute one for the other without noticing |
| P240 | 220 | 58.5 µm | The first grit of the finishing range rather than the preparation range, and the first where the two scales visibly part company: P240 falls between CAMI 220 and 240 and matches neither |
| P280 | 240 | 52.2 µm | Fine finishing on hardwood, and between coats of varnish |
| P320 | 280 | 46.2 µm | De-nibbing between coats |
| P400 | 320 | 35 µm | The clearest case of the mismatch |
| P500 | 360 | 30.2 µm | Fine finishing and light wet sanding |
| P600 | 400 | 25.8 µm | Wet sanding paint and polishing metal |
Frequently asked questions
Is P320 the same as 320 grit?
No. P320 is roughly CAMI 280 — the American 320 grit is finer than the European P320. The two scales agree up to about 180 and separate above it, so at this end a packet marked 320 and a packet marked P320 are genuinely different papers.
What grain size is P320?
An average grain of 46.2 µm — 0.046 mm. That figure is what the P number is defined by, which is why it is the reliable way to compare across scales.
What is P320 used for?
De-nibbing between coats. A P320 packet and a 320 packet are not the same paper: P320 is nearer CAMI 280.
What comes before and after P320?
Coming up from coarse, P280 (52.2 µm) and then this; the next step finer is P400 at 35 µm. Skipping more than one step leaves scratches the finer paper cannot remove — the usual cause of a surface that looks fine dry and terrible once finish goes on.