Sandpaper Grit Guide

Walk into any hardware store and you'll find sandpaper labelled 40, 80, 120, 240, 400, 2000 — sometimes with a P in front of the number, sometimes without. No explanation of what those numbers mean, what the P indicates, or why two packs labelled "400 grit" from different brands can produce visibly different results on the same surface.

This guide explains the system — grit numbers, abrasive minerals, backing materials, and the sequences that produce the right result for the job in front of you.

What the grit number means

The grit number refers to the number of abrasive particles per square inch on the sandpaper surface — determined by the mesh size used to sieve and grade the abrasive particles. A higher number means smaller particles were passed through a finer mesh. Smaller particles cut less aggressively and leave a smoother surface.

Higher grit = finer abrasive = smoother finish. Lower grit = coarser abrasive = faster material removal.

This trips up beginners consistently. "Higher" feels like it should mean coarser, because higher-grit tools (angle grinders, drill speeds) are associated with more power. Sandpaper works the opposite way.

The two grit systems: CAMI and P-grade (FEPA)

There are two grading standards for sandpaper abrasives in common use: CAMI (Coated Abrasive Manufacturers Institute — North American standard) and P-grade (FEPA — Federation of European Producers of Abrasives, the international standard used in Australia). Most abrasives sold in Australia are labelled in P-grade. CAMI grading still appears on some imported US-brand packs and older workshop stock.

At coarse grits, the two systems are nearly identical. At fine grits, the gap becomes significant:

Abrasive minerals

The abrasive particle determines how the paper cuts, how long it lasts, and what surfaces it suits. Five minerals are in common use on coated abrasives available in Australia:

Practical note for most users: Aluminium oxide is the default for wood and general metal work. Silicon carbide is the correct choice for wet sanding and non-ferrous metals. Garnet earns its place for final bare-timber hand sanding where the smoothness of the finish justifies the shorter life. You will rarely need zirconia or ceramic in sheet form — those minerals are most useful in high-speed belt and disc applications.

For hook-and-loop sanding disc and fibre disc selection (with the abrasive grain golden rule by metal type), see our Sanding Disc & Abrasive Disc Guide. For overlapping flap disc abrasives, see our Flap Disc & Abrasive Guide — the selection logic for grinder applications is different.

Backing materials

The backing is what the abrasive is bonded to. It determines flexibility, tear resistance, heat tolerance, and whether the paper can be used wet. Backing weight is denoted by a letter.

Sandpaper forms

The physical format of the sandpaper must match the tool and the task. Using the right abrasive mineral in the wrong form is a common source of poor results and wasted material.

Note on flap discs and grinding discs for angle grinders: These are covered separately in our Flap Disc & Abrasive Guide. The selection logic, safety requirements, and abrasive performance at grinder speeds are substantially different from the sheet, roll, and disc applications covered here.

Grit sequence guide: bare timber

Timber finishing is where grit sequence discipline matters most. Each grit removes the scratch marks from the previous grit. If you skip a grade, you leave deeper scratches in the surface that become visible — often dramatically so — once stain, oil, or clear coat is applied.

Standard bare timber sequence (furniture, joinery, cabinetry)

P80 → P120 → P180 → P220

Start at P80 if the surface has rough spots, milling marks, or light cupping. For pre-surfaced timber with minimal defects, starting at P120 is appropriate. Do not go below P80 on power tools unless you are genuinely shaping material. Finish at P220 before applying any water-based finish, stain, or oil. For oil-based finishes, P180 is often the finishing grade — coarser scratches give the oil more surface area to penetrate.

Between coats of paint or varnish (timber)

P320–P400 (very light touch)

The purpose is to knock back grain raise and minor dust nibs — not to remove material. Use a sanding block for flat surfaces. Work with the grain. Vacuum and wipe with a tack cloth before recoating.

Timber floors (drum sander)

First cut on badly cupped or heavily finished boards: P40 at a slight angle across the grain. Second pass along the grain: P60–P80. Final belt pass: P100–P120. Always hand-sand the edges with a matching grade — floor edge sanders are a common source of visible circular scratches that the drum doesn't reach.

Softwood vs hardwood

Softwoods (pine, radiata) raise grain more aggressively under water-based products. After P220, raise the grain deliberately with a damp cloth, let it dry, then lightly resand at P220 before applying the first coat. This avoids a rough surface after the first water-based coat.

Grit sequence guide: metal

Metal sanding has two distinct end goals: surface preparation for coating (paint, powder coat, or plating), and surface finishing for appearance (polished, brushed, or mirror finish). The sequences are different.

Mild steel — surface prep for paint

P80 → P120 → P180 → P240

Start at P80 to remove mill scale, rust, and old coating. Progress through the grades. Finish at P240 minimum for primer adhesion — a surface that is too smooth (finer than P240) can reduce paint adhesion. After sanding, remove all abrasive residue before priming.

Stainless steel — surface finishing

Stainless steel is typically worked to a specific surface finish designation. The most common:

• Brushed/satin (2B equivalent): P120–P150 with a constant unidirectional stroke using an aluminium oxide or ceramic belt. Direction must be consistent — random or orbital marks are visible on stainless.
• Mirror/polished: P180 → P240 → P320 → P400 → P600 → P800 → P1200, then buffing compound. Each grade must fully remove the previous grade's scratches before progressing.

Cross-contamination warning: Do not use the same abrasive on mild steel and stainless steel. Iron particles embedded in the abrasive will contaminate the stainless surface and cause rust staining within days. Keep separate sandpaper for stainless, clearly labelled.

Aluminium

Aluminium loads standard aluminium oxide paper quickly. Use silicon carbide paper or aluminium oxide with a stearate (anti-loading) coating for aluminium. Dry sanding aluminium creates fine, highly flammable dust — good dust extraction is essential. For wet sanding aluminium, silicon carbide on film or waterproof backing is the standard choice.

Cast iron

Aluminium oxide handles cast iron well. Cast iron dust is fine and dark — a nuisance and a contamination risk on other surfaces. Sand in a controlled area and clean up thoroughly before moving to other materials.

Grit sequence guide: automotive paint and clear coat

Automotive wet sanding is a distinct discipline from workshop or furniture sanding. The goal is to level orange peel texture in clear coat (or colour coat) before polishing to a high gloss. All sanding at these grades is done wet — water is the lubricant and swarf-clearing agent.

Correcting orange peel in clear coat

P1000–P1500 (wet) → P2000 (wet) → P3000 (wet) → polishing compound

Start at P1000–P1200 to flatten the orange peel texture. Progress to P1500 to refine the P1000 scratches. Move to P2000 to prepare the surface for polishing. P2500–P3000 is used for final scratch refinement before machine polishing. Each grade should fully eliminate the previous grade's scratches before progressing — hold the surface at a 45° angle under direct light to check.

Levelling a paint run

Feather the run with P800 or P1000 (wet) to level without cutting into adjacent good paint. Progress through P1200 → P1500 → P2000, then polish.

Sanding between primer coats (automotive)

P400–P600 (dry) or P600–P800 (wet)

Keying between primer coats: P400–P600 dry is standard. Wet sanding with P600–P800 is used where a finer surface is needed before colour coat. After wet sanding, allow the panel to dry fully (minimum several hours) before recoating — trapped moisture under paint causes blistering.

Grit guide: plaster, render, and pre-paint prep

Plasterboard (drywall) and wet-applied plaster have specific requirements. The surfaces are relatively soft, they clog abrasives quickly, and the dust is fine and heavy — extract it or it goes everywhere.

Plasterboard joins, set, and fill

P80–P120 to level, P180–P220 final pass

Sand set and fill with P120 to level without cutting into the board paper facing. Move to P180–P220 for the final pass before priming. Sanding through the paper facing on plasterboard (visible as a fuzzy surface) creates a weak spot under paint — reduce pressure and check frequently.

Wet-applied plaster and render

P60–P80 (coarse imperfections), P120 final

Render is harder than plasterboard compound — it can handle more aggressive starting grits for levelling runs or trowel marks. Do not use a power sander on fresh, soft plaster — let it cure fully first. Hand sanding with a block is standard for most plaster work. P120 before priming is typically sufficient for render.

Keying a painted surface for recoating

P220–P320 (light scuff)

The objective is deglossing to improve adhesion, not material removal. A light pass with P220–P320 scuffing paper is sufficient for most interior paints. Liquid sandpaper (chemical deglosser) is an alternative for this step — see below.

Wet and dry sandpaper

"Wet and dry" is a specific product designation — not a description that applies to all sandpaper. Wet and dry paper is silicon carbide abrasive on a waterproof backing (film or resin-treated paper) designed for use with water as a lubricant. Water keeps the surface cool, prevents the abrasive from loading with swarf, and floats away the removed material so it does not re-scratch the surface.

When to use wet and dry paper:

• Automotive clear coat and lacquer finishing (P1000 and finer)
• Glass edge polishing
• Ceramic and stone surface finishing
• Non-ferrous metals (aluminium, brass, copper) where a wet process is preferred

When not to use wet and dry paper:

• Timber — water raises the grain and can cause swelling and staining
• Bare steel — water causes surface rust within hours
• Anywhere you cannot manage the water and resulting slurry safely

Liquid sandpaper (chemical deglosser)

Liquid sandpaper — sold under brand names including Intergrain, Dulux Prep, and similar — is not abrasive. It is a solvent-based chemical that etches a glossy painted surface to improve adhesion for the next coat, without mechanical sanding. It removes the gloss chemically. It is useful for surfaces with complex profiles where hand-sanding is impractical, or as a preparation step on sound paintwork in good condition. It does not level imperfections, fill grain, or replace sanding on bare timber or heavily weathered surfaces.

Sanding discs for random orbital sanders: sizing and attachment

Random orbital sanders (ROS) produce a random oval orbit that prevents the circular scratch marks left by standard orbital sanders. They are the standard choice for furniture, cabinet, and automotive panel finishing. Getting the disc size and attachment type right is critical — the wrong size disc will not attach correctly and can detach under load.

Disc sizes in the Australian market

• 115mm: Quarter-sheet orbital sanders and some small detail sanders
• 125mm: Common on mid-size random orbital sanders (Bosch, Makita, Milwaukee 5" range)
• 150mm: Larger random orbital sanders, standard for automotive bodywork and cabinet finishing

The disc diameter must match the sander pad diameter exactly. Using a 125mm disc on a 150mm pad leaves the edge unsupported and the disc will tear. Using a 150mm disc on a 125mm pad is a safety risk — the overhanging edge can catch on the workpiece.

Dust extraction holes

Most random orbital sander discs have a hole pattern that aligns with the sander's dust extraction ports. Common patterns include 6-hole, 8-hole, and 15-hole (Festool Rotex/ETS compatible). Using a disc with a non-matching hole pattern on an extraction sander does not damage anything, but dust extraction performance will be poor. For mesh/net discs, extraction is through the open backing itself and standard holes are not required.

Hook-and-loop vs PSA

Hook-and-loop (Velcro-style): The dominant attachment method in AU. The disc has a loop backing; the sander pad has a hooked surface. Discs can be removed and replaced quickly and are repositionable. Standard for workshop and automotive use.

PSA (Pressure-Sensitive Adhesive): Peel-and-stick. Once applied, the disc is fixed until removed — removal is more difficult and the adhesive backing can leave residue on the pad. Less common in Australia than hook-and-loop, but still found on some older sanders and certain production finishing applications where disc migration is a concern.

The one mistake that ruins a finish: skipping grits

Each grit leaves a characteristic scratch pattern in the surface. The function of the next grit is to cut away those scratches and replace them with finer ones. If you jump from P80 to P220, you are trying to use P220 particles to remove P80-depth scratches — they are not large enough to do it efficiently, and you will spend more time sanding than if you had followed the sequence.

The real cost is invisible until finishing. P80 scratches left in a surface that has been sanded to P220 will be visible once stain or clear coat is applied. Stain fills and darkens the scratches, making them appear as dark streaks or lines. Clear coat amplifies the scratch texture by adding reflective depth above it.

The rule: When moving up the grit sequence, move one step at a time. Each grade should fully remove the previous grade's scratches before you progress. Check by sanding one direction at each grade, then sanding the next grade at 90° — when the previous scratches are gone, you can progress.

You can skip grits when moving down (using a finer grit partway through the sequence to start a new job), but never when moving up toward a finished surface.

Frequently asked questions about sandpaper

What do the grit numbers on sandpaper mean?

The grit number represents the particle size of the abrasive — specifically, the mesh size used to sieve and grade the abrasive particles. Higher numbers mean smaller particles (finer abrasive, smoother finish); lower numbers mean larger particles (coarser abrasive, faster material removal). P40 is coarse and aggressive; P2000 is ultra-fine for polishing clear coat.

What is the difference between CAMI and P-grade grit systems?

CAMI is the North American grading standard; P-grade (FEPA) is the international standard used in Australia. At coarse grits (P40–P180), the two systems produce nearly identical particle sizes. At fine grits, they diverge significantly — CAMI 400 is equivalent to approximately P800, meaning a CAMI 400 product is far finer than a P400 product. Most sandpaper sold in Australia is P-grade. P-grade products will have the "P" prefix before the number on the label.

What grit sandpaper should I use on bare wood before painting?

For bare timber before painting, finish at P180–P220. A typical sequence for rough timber is P80 → P120 → P180 → P220. For pre-surfaced or planed timber, starting at P120 is sufficient. Do not finish coarser than P180 for painted surfaces — coarser scratches may show through paint, particularly with water-based products. Sand with the grain on the final pass.

What grit sandpaper should I use between coats of paint?

P320–P400 for between-coat keying on most interior and exterior paints and varnishes. For automotive between-coat sanding (base coat keying): P400–P600 dry or P600–P800 wet. The goal is deglossing and levelling minor imperfections, not material removal — use a light touch and a sanding block on flat surfaces.

What is wet and dry sandpaper used for?

Wet and dry sandpaper (silicon carbide on waterproof film or paper backing) is used wherever water as a lubricant benefits the process: automotive clear coat and lacquer wet sanding (P1000–P3000), glass edge polishing, ceramics, and non-ferrous metals. Water keeps the abrasive cool, prevents loading, and floats away swarf. Standard aluminium oxide paper on paper backing cannot be used wet — it absorbs water and disintegrates.

What is the difference between aluminium oxide and silicon carbide sandpaper?

Aluminium oxide is tougher and longer-lasting — the standard choice for timber, mild steel, and general use. It self-fractures under load, exposing new cutting edges. Silicon carbide is harder and sharper but more brittle — the correct choice for wet sanding, glass, ceramics, hard plastics, and non-ferrous metals. Silicon carbide cuts more aggressively on hard smooth surfaces but wears faster on abrasive or fibrous materials like timber.

Can I use the same sandpaper on both wood and metal?

The same abrasive type (aluminium oxide) works on both timber and metal. The concern is cross-contamination: metal particles embedded in sandpaper used on timber can leave dark staining in timber grain; iron particles transferred from sandpaper used on mild steel will contaminate stainless steel and cause rust staining. Keep separate sandpaper for ferrous metals and non-ferrous materials / timber, clearly labelled.

What grit sandpaper do I need for automotive clear coat wet sanding?

For correcting orange peel in clear coat: P1200–P1500 (wet) to flatten, P2000 (wet) to refine, P2500–P3000 (wet) before machine polishing. Use silicon carbide on film or waterproof backing — standard paper disintegrates wet. For levelling paint runs: start at P800–P1000, progress through P1500 → P2000 before polishing. Check progress under directional light at each stage before moving to a finer grade.

What does hook-and-loop mean on sanding discs?

Hook-and-loop attachment is a Velcro-style system: the sander pad has small hooks; the sanding disc has a loop (soft) backing that attaches to the hooks. Discs can be attached, removed, and replaced quickly without tools. Hook-and-loop is the dominant disc attachment system in Australia for random orbital and detail sanders. The disc diameter must match the sander pad exactly — 115mm, 125mm, and 150mm are the common sizes in the AU market.

Why shouldn't I skip grits when sanding?

Each grit removes the scratches left by the previous grit. If you skip from P80 to P220, you are asking fine particles to remove deep scratches — they are too small to do it efficiently, and the scratches remain. Under stain, oil, or clear coat, those scratches become visible as streaks, dark lines, or a rough texture in the finish. Work through the grades in sequence. At each stage, the surface should show only the scratch pattern of the current grade before you progress.

What grit sandpaper should I use on plaster before painting?

P120 to level joins, fill, tool marks, and surface imperfections. P180–P220 for the final pass before priming. On plasterboard specifically, avoid cutting through the paper facing — sand with moderate pressure and check frequently. For wet-applied plaster and render, P80 can be used to address significant imperfections before progressing to P120. Apply primer before topcoat — bare plaster and render are highly porous and will produce an uneven topcoat finish without it.

What is garnet sandpaper used for?

Garnet is a natural abrasive mineral — soft, orange-red, and not long-lasting compared to aluminium oxide or silicon carbide. It is used primarily for final hand-sanding on bare timber (furniture, joinery, cabinetry) where an exceptionally smooth surface is the goal before staining or oiling. Garnet fractures to leave a smooth cut, and produces less raised grain on bare timber than aluminium oxide. It is not suited to power sanding (wears too quickly) or to metal (not hard enough). Bunnings stocks garnet paper in the fine grades (P120–P220); specialist woodworking suppliers carry finer grades.

Sandpaper and abrasives from AIMS Industrial

AIMS Industrial supplies a full range of abrasives for trade and industrial use: aluminium oxide and silicon carbide sheets, rolls, belts, and hook-and-loop sanding discs in the full grit range from P40 through P3000.

Related guides:

• Flap Disc & Abrasive Sanding Guide — abrasive minerals for angle grinder discs and fibre discs
• Drill Bit Types Guide — drill bit selection for metalwork, timber, masonry, and tile

Browse our abrasives range or contact us for volume pricing on industrial abrasive supplies.