Lower number = coarser paper, bigger scratches, faster cutting. Higher number = finer finish. Here's what each grit is actually for, and the sequence that gets you to a clean finish.
| Grit (CAMI) | Class | What it's for | ≈ FEPA |
|---|---|---|---|
| 40–60 | Coarse | Heavy stripping — paint, rust, rough shaping, floor sanding first pass | P40–P60 |
| 80 | Med-coarse | First pass on bare wood; levelling deep scratches and mill marks | P80 |
| 100–120 | Medium | General smoothing; the workhorse range for most wood sanding | P100–P120 |
| 150–180 | Med-fine | Final pass on bare wood before stain or paint; softwood pre-finish | P150–P180 |
| 220 | Fine | Final pass before clear finish; light scuff between coats | P220 |
| 320 | Extra fine | Sanding between finish coats; smoothing raised grain | P400 |
| 400–600 | Super fine | Wet-sanding finishes; metal prep before polish | P800–P1200 |
| 800–1000 | Ultra fine | Wet colour-sanding automotive clear coat | P1500–P2000 |
| 1500–2000 | Polishing | Final wet sand before buffing and compound | P2500+ |
CAMI (US) and FEPA "P" (European) scales match closely up to ~220, then diverge — a P400 is about a US 320. Above 220, check which scale your paper uses before jumping grits.
80 for rough or milled lumber, 120 if the surface is already decent. Then step 120 → 180 → 220 and stop — sanding bare wood past 220 can burnish it and hurt stain absorption.
P is the European FEPA scale, plain numbers are US CAMI. They're nearly identical up to ~220, then split: P400 ≈ US 320, P800 ≈ US 400–600. Above 220, confirm the scale before choosing.
Skipping one step (80 → 150) costs you more time than it saves — the finer paper takes ages to erase the coarse scratches. Each grit should only have to remove the previous grit's pattern.
220–320, just enough to knock down dust nibs and give the next coat something to grip. Wet-sand 400+ for a fine sprayed finish.