Sandpaper looks simple — rough paper, higher number means smoother — but the numbering hides real complexity: different abrasive minerals, different numbering standards, and progressions that make or break finishes. Buy wrong and you either sand forever or scratch what you meant to smooth.
This guide explains what grit numbers actually measure, which abrasive types suit which jobs, and the progressions professionals use for wood, metal, and between-coat work.
What grit numbers measure
Grit number counts abrasive particles per square inch of the grading screen: higher number, smaller particles, finer scratches. The scale runs from brutally coarse (24–36, for paint stripping and heavy shaping) through medium (80–120, general smoothing) and fine (150–220, finish prep) to ultra-fine (320+, between-coat scuffing and polishing).
Two numbering standards exist — CAMI (US) and FEPA (European, marked “P”) — which diverge at fine grits: P220 is roughly CAMI 220, but the correspondence isn’t exact at the extremes. For woodworking’s common range the difference is negligible; just be consistent within a project.
Abrasive types: garnet, aluminum oxide, silicon carbide
Garnet (reddish-brown paper) is the traditional wood abrasive: cuts fast initially, dulls relatively quickly — fine for hand sanding, poor value for power sanders. Aluminum oxide (tan/brown) is the workhorse: durable, versatile, the right default for wood on power sanders. Silicon carbide (dark gray/black) is harder and sharper: the choice for wet-sanding finishes, glass, and metal, but it dulls fast on raw wood.
Ceramic abrasives (often blue/purple) are the premium option for aggressive stock removal — they self-sharpen as they wear and last dramatically longer on belt sanders. Zirconia sits between aluminum oxide and ceramic for heavy grinding. Match the mineral to the job; it’s as important as the grit number.
Progressions for common jobs
Raw wood to finish: 80 (if rough) → 120 → 150 → 180 → 220. Never skip more than one step — each grit erases the previous grit’s scratches. Stripping old finish: 60–80 → 120 → 150. Between finish coats: 220–320, scuff only. Metal deburring: 80–120 aluminum oxide or zirconia. Polishing: silicon carbide wet-sanding 400 → 600 → 800+.
The universal mistake is jumping too far (80 straight to 220) or sanding finer than needed (400 on raw wood before finish can impair adhesion). Our Random Orbital Sander Guide: Grits, Speeds, and Swirl-Free Finishes on orbital sander technique shows the progression in action. Write the sequence on the project, not in your head.
Hand sanding vs. power sanding
Power sanders do the flat-field work; hand sanding (with a block, never bare fingers — fingers create pressure spots and uneven surfaces) handles contours, edges, and final passes. Always sand with the grain on the final grits; cross-grain scratches from coarse stages must be fully removed by subsequent with-grain passes.
Sanding sponges and contoured blocks conform to profiles and moldings where rigid blocks can’t reach. For the final pass before finish, many finishers hand-sand with the last grit after power sanding — it catches the subtle defects machines miss.
When sandpaper is done
Abrasives dull: cutting slows, dust output rises, and the paper looks shiny or clogged. Clogged paper (“loading”) can be partially revived with a cleaning stick (gum rubber) — worth it for premium discs. But don’t nurse dead paper: the time cost dwarfs the replacement cost, and dull abrasive causes heat, burning, and the temptation to press harder (which causes defects).
Store paper dry and flat; humidity degrades the adhesive and backing. And buy in the quantities you’ll actually use — a 100-pack of a grit you’ll touch twice a year is just expensive clutter.
Wet sanding: when and how
Wet sanding — sanding with water or soapy water as lubricant — is the technique for finishes and ultra-smooth surfaces: between-coat leveling, rubbing out finishes, and polishing. Use silicon carbide paper (designed for wet use), keep the surface wet, and sand lightly — the water carries away waste, prevents clogging, and produces a finer scratch pattern.
Never wet-sand raw wood (it raises grain and can stain); reserve it for cured finishes, metal, and solid-surface materials. Wipe and inspect frequently — wet surfaces hide progress. It’s a finishing technique, not a stock-removal one, and it produces the glass-smooth results that dry sanding can’t quite reach.
Sanding sealers and grain raising
Two pro techniques that elevate results. Grain raising: dampen raw wood lightly, let it dry, then sand off the raised fibers with your final grit — this pre-raises the grain so the finish doesn’t do it for you (causing roughness in the first coat). Essential for water-based finishes.
Sanding sealers: thin first coats that seal the wood, making subsequent sanding easier and finishes more even — particularly valuable on blotch-prone woods and end grain. They’re an extra step that pays off in finish quality, especially for beginners whose technique isn’t yet compensating for difficult wood.
Economics of abrasives: buying smart
Abrasives are consumables — budget for them like sandpaper, not like tools. Buying in bulk (50/100-packs of your common grits) cuts per-disc cost dramatically; the savings fund the “change discs often” habit that actually improves results. Premium abrasives (ceramic, quality aluminum oxide) cost more per disc but cut faster and last longer — often cheaper per project than bargain paper that dies fast.
Track what you actually use: most shops burn through 80, 120, and 220 and barely touch the exotic grits. Stock deep on the workhorses, shallow on the specialists. And date your bulk packs — old adhesive fails, and a drawer of dead discs is money already wasted.
Abrasive selection table: material by task
Raw softwood, stock removal: ceramic or zirconia, 40–60 grit. Raw softwood, smoothing: aluminum oxide, 80–150. Raw hardwood, smoothing: aluminum oxide, 80–220 progression. Finish prep (all wood): aluminum oxide or garnet (hand), 150–220. Between coats: silicon carbide or aluminum oxide, 220–320, or sanding sponges.
Paint stripping (wood): ceramic or zirconia, 40–80. Bare metal, deburring: zirconia or aluminum oxide, 60–120. Metal pre-paint: aluminum oxide, 120–220. Wet-sanding finishes: silicon carbide, 400–2000, waterproof backing. Glass/plastic polishing: silicon carbide wet, fine grits.
Backing notes: paper for hand and finish sanding; cloth for belts and heavy machine use; film for ultra-consistent fine finishing; sponges for contours. Match all three variables — grit number, abrasive mineral, backing — to the task, and abrasives stop being mysterious. They’re a system with three dials; most people only turn one.
Glossary: abrasive terms
Aluminum oxide: the workhorse abrasive — durable, versatile, the right default for wood on power sanders.
Backing: the paper, cloth, film, or sponge carrying the abrasive — matched to the application (cloth for belts, film for fine finishing).
CAMI/FEPA: the US and European grit numbering standards — close through most of the woodworking range, divergent at fine extremes; stay consistent within a project.
Ceramic: premium self-sharpening abrasive for aggressive stock removal — dramatically longer-lived on belt sanders.
Closed vs. open coat: abrasive coverage density — open coat resists clogging on soft materials; closed coat cuts faster on hard ones.
Garnet: traditional natural abrasive — cuts fast initially, dulls quickly; fine for hand sanding, poor for power.
Grit number: particles per inch of grading screen — higher number, finer scratch. The scale’s only job is ordering coarseness.
Silicon carbide: hard, sharp abrasive for wet-sanding finishes, glass, and metal — dulls fast on raw wood.
Stearate coating: the anti-loading treatment on many sandpapers — resists clogging, extends disc life.
Zirconia: tough abrasive between aluminum oxide and ceramic — excellent for heavy grinding and metal.
Decision summary: the abrasive system
Stock three minerals: aluminum oxide for general woodwork (your 80/120/150/220), ceramic for belt-sander aggression, silicon carbide for wet-sanding finishes. Stock the workhorse grits deep (80, 120, 220) and specialists shallow. Buy in bulk for the common grits — the per-disc savings fund the change-often habit.
Operating rules: match mineral and grit to the task via the selection table; never skip more than one grit; change paper when cutting slows; store dry and flat. Abrasives are consumables — treat them as a budgeted supply, not a purchase to agonize over. The shops with the best finishes aren’t the ones with the fanciest paper; they’re the ones that change it without hesitation.
One last rule: respect the scratch pattern
Every sanding job ends the same way: with the scratch pattern of your final grit, and nothing else. Before you call any surface done, inspect it in raking light — a work lamp held low across the surface reveals stray coarse scratches, pigtails, and dish-outs that overhead light hides. If you find a defect, drop back two grits and work forward again; trying to polish out a deep scratch with fine paper just wastes time.
This final inspection takes thirty seconds and separates professional-looking results from almost-there ones. The abrasive system — right mineral, right grit, full progression, fresh paper — does the work; the inspection proves it. Make raking-light checks a reflex, and your finishes will show it.
Frequently asked questions
What grit should I start with on rough lumber?
80 grit for genuinely rough or mill-marked stock, 100–120 if it’s already fairly smooth. Starting too fine just wastes time; starting too coarse leaves deep scratches to remove.
What’s the difference between P220 and 220?
P-numbers are the European FEPA standard, plain numbers the US CAMI standard. They align closely through most of the woodworking range but diverge at very fine grits. Within one project, stick to one standard.
Can I reuse sandpaper?
Lightly used paper for a second pass at the same grit is fine. But once cutting slows or the paper clogs, replace it — dull abrasive costs more in time and defects than new paper costs in money.
Which abrasive is best for metal?
Aluminum oxide or zirconia for general metal work; silicon carbide for wet-sanding and polishing. Use dedicated metal abrasives — wood paper loads up and underperforms on metal.
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