Sandpaper Grit Guide

Grab the wrong grit and you’ll either spend an afternoon polishing scratches you can’t see or gouge a fresh cabinet door beyond saving. The number printed on the back of the sheet is the whole game — it tells you how fast it cuts and how smooth it leaves things.

How grit numbers actually work

Grit is a count of abrasive particles per square inch of the sheet. A low number like 40 or 60 means big, sparse particles that dig deep and remove material fast — and leave deep scratches behind. A high number like 320 means tiny, densely packed particles that barely cut but leave a glassy surface. That’s the whole trade-off: aggression versus smoothness. You work down the ladder from coarse to fine, and each pass erases the scratches left by the grit before it.

Most sandpaper sold in North America uses the CAMI scale (the plain numbers you already know). European sheets use the FEPA “P” scale, printed as P80, P120, and so on. They track closely in the coarse and medium ranges but diverge in the fine grits — P400 is finer than a CAMI 400. Whichever system you’re holding, the principle is identical: pick your starting grit for the mess you’re facing, then step up. A full range of sandpaper and sanding sheets in both scales lives in one place, so you’re not hunting for the missing middle grit halfway through a job.

The grit ranges, decoded

Here’s the map most projects run on. Think of it as four neighborhoods — coarse for demolition, medium for shaping, fine for prep, and extra-fine for finishing.

Tip: for raw wood, stopping at 180–220 is the sweet spot before staining. Go finer than that and you burnish the grain closed, so it won’t drink up the stain and finish evenly — you’ll get a blotchy, washed-out color.

Match the grit to the material

Wood is only half the story. Drywall, metal, and painted surfaces each want a different starting point. Sand drywall joint compound with 120–150 — anything coarser tears the paper facing. For bare metal and rust, start around 80 and climb; for a scuff coat before repainting trim, 220 is plenty. When you’re knocking down a repair with wood filler or patching compound, let it cure fully, then hit it with 120 to feather the edges flush before your final 180–220 pass.

• Bare softwood (pine, fir): 80 → 120 → 180. Softwoods fuzz up, so don’t overwork them.
• Hardwood (oak, maple, walnut): 100 → 150 → 220 for a stain-ready surface.
• Old painted or varnished furniture: 60–80 to strip, then step up as the finish disappears.
• Drywall mud & skim coats: 120–150 only, with a light touch and a sanding sponge.
• Between clear coats: 320–400, wiped clean before the next coat goes on.

By hand or by machine — and the abrasive itself

A random-orbit sander is the single best upgrade for anyone who sands more than once a year — it cuts fast without leaving swirl marks, and hook-and-loop discs swap in seconds. DeWalt, Makita, Bosch, and Ryobi all make solid 5-inch models, and you’ll find them alongside the discs in the power-tool lineup. Detail and finish sanders handle corners and spindles a disc can’t reach. But keep hand sheets and sanding blocks around too — profiles, edges, and final passes still go better by hand, and a cork or rubber block keeps your surface dead flat.

The abrasive mineral matters as much as the grit. Aluminum oxide is the everyday all-rounder for wood. Silicon carbide (the gray-black paper) is harder and self-sharpens — it’s what you want for metal, drywall, and wet-sanding finishes. Ceramic abrasives, like the 3M Cubitron discs, cost more but cut faster and last far longer on a machine, which pays off on big jobs. Zirconia sits in between and shrugs off heat on power tools. Stock a spread of grits and a couple of mineral types from the sanding and abrasives aisle and you’ll rarely stall mid-project.

Pick by your project

Frequently asked questions

Still not sure which grit to reach for on your project? The folks at your local independent hardware store sand for a living and will point you to the right sheet in ten seconds — or you can ask us here.