Quick answer: A "P" in front of a grit number (P120, P400) means the paper is graded to the European FEPA standard; a plain number (120, 400) means the North American CAMI standard. Up to about 220 the two scales are close enough to treat as the same. Above that they diverge fast – P400 is about CAMI 320, P800 is about CAMI 400, and P1200 is about CAMI 600 – because FEPA holds a tighter tolerance on particle size and numbers its fine grades differently. Check the letter before you compare fine-grit paper from two suppliers.
What the terms mean
- FEPA – the Federation of European Producers of Abrasives, headquartered in Paris. FEPA sets European standards for grain, backing and every other aspect of abrasives. Products graded to it carry the "P" prefix, so "P-grade" and "FEPA grade" mean the same thing. Most European-made abrasives – and much of what's sold in the US today – are P-graded.
- CAMI – the Coated Abrasives Manufacturers Institute, the North American counterpart, based in Cleveland, Ohio. US manufacturers belong to CAMI, and the traditional plain grit numbers on American sandpaper follow its standard. Several manufacturers belong to both.
- JIS – the Japanese Industrial Standard, seen on Japanese waterstones and some polishing papers. Its numbers run higher again at fine grits.
Why the scales differ
Both scales grade grain by particle size, but they define the size ranges differently. FEPA's "P" scale allows a narrower spread of particle sizes within each grade, so a P-grade paper leaves a more uniform scratch; CAMI grades allow a wider spread. At coarse and medium grits the average particle size lines up closely, but from around 240 upward the two scales number their grades on different curves, and the same number can mean a noticeably different scratch. A P600 is much finer than a CAMI 600 – roughly the equivalent of a CAMI 360.
CAMI vs. FEPA conversion chart
| CAMI (US) | FEPA (P) | Average particle size | Typical use |
|---|---|---|---|
| 36 | P36 | ~530 µm | Heavy stock removal |
| 40 | P40 | ~425 µm | Coarse shaping, stripping |
| 60 | P60 | ~265 µm | Coarse sanding |
| 80 | P80 | ~200 µm | Leveling, removing planer marks |
| 100 | P100 | ~160 µm | Medium sanding |
| 120 | P120 | ~125 µm | Medium sanding |
| 150 | P150 | ~100 µm | Smoothing |
| 180 | P180 | ~80 µm | Fine sanding |
| 220 | P220 | ~68 µm | Final sanding before finish |
| 240 | P280 | ~52 µm | Between coats |
| 280 | P320–P360 | ~44 µm | Between coats |
| 320 | P400 | ~35 µm | Fine finishing, wet sanding |
| 360 | P500 | ~30 µm | Wet sanding |
| 400 | P800 | ~22 µm | Wet sanding, polishing |
| 500 | P1000 | ~18 µm | Wet sanding, polishing |
| 600 | P1200 | ~15 µm | Wet sanding, polishing |
| 800 | P1500–P2000 | ~12 µm | Automotive clear coat |
| 1000 | P2000 | ~10 µm | Automotive clear coat |
| 1200 | P2500–P3000 | ~8 µm | Final polish before compound |
Particle sizes are approximate averages; each grade spans a range. Values above 220 vary slightly between published tables.
What it means in practice
- Coarse and medium grits (to 220): treat CAMI and P numbers as interchangeable.
- Fine grits: convert before you compare. If your finishing schedule calls for 320 and the box says P320, you're using a coarser paper than you think – P400 is the match.
- Grit sequences: when you step through grits, stay on one scale. Mixing a CAMI 220 with a P320 is a smaller step than it looks; a CAMI 320 to a P800 is a bigger one.
- Uniformity: P-grade paper's tighter particle spread gives a more consistent scratch pattern, which matters most in finishing and wet sanding.
Most of what we sell is made to FEPA "P" grades, and our product pages say which. If you're matching an existing schedule and aren't sure, ask – we'll tell you which grade to order. See our abrasives dictionary for other terms, and wet sanding explained for fine-grit sequences.
