Sandpaper Grit Guide: What to Use on Wood and Between Finish Coats

The right sandpaper depends on both the material and the job. Rough hardwood, softwood ready for stain, a dry coat of polyurethane, and painted furniture need different treatment. A higher grit number means a finer abrasive, but it does not automatically mean better preparation.

A new shelf may need only two or three sanding steps, while an old painted cabinet needs a different starting point. Check the surface first, then read the instructions for your stain, paint or finish before choosing where to stop.

Sandpaper grits at a glance

These are possible uses, not a sequence every project must follow. The P prefix means FEPA grading. Norton's material-by-material guide explains how the task changes as you move from removal to smoothing and finishing.

Other grading standards also exist. Matching numbers are not always equivalent, especially among finer abrasives, as Mirka's comparison chart shows. Manufacturer examples below retain the maker's own grit wording: a US label saying “400” should not automatically become “P400.”

Choose your final grit before you start

Read the preparation instructions first. For example, General Finishes distinguishes hardwoods from softwoods: its guidance for maple and oak stops at 150 for oil-based stains or 180 for water-based stains. For pine and alder, it allows 180 and 220 respectively. “Hardwood” does not automatically mean start with P80, and “softwood” does not mean stop at P120.

Oil finishes deserve particular attention. Rubio Monocoat recommends 120 grit, or a maximum of 150, for Oil Plus 2C. The P400 oil-finish entry describes specialist work where the product permits it; it is not advice to polish bare wood before oiling.

Enamel, latex and acrylic paints also have their own preparation and primer requirements. P120 or P180 may be part of preparing the underlying wood, but neither number guarantees readiness for every paint. Try the complete sanding, primer and paint system on an offcut before treating the visible surface.

Build a short sanding sequence

Suppose you are using FEPA paper, your finish allows P180, and your new solid-wood board is reasonably smooth. A sequence of P120 → P150 → P180 is a sensible starting plan. If P120 does not remove the rough marks effectively, use a coarser grit where needed before working back through finer grades. Add P220 only when the finish instructions call for it.

At each stage, remove the scratches left by the previous abrasive before moving on. A finer sheet should refine an even surface; it should not spend the entire session trying to erase deep marks. As Rubio's furniture preparation guide advises, hand-sand with the grain and avoid pressing hard to make a worn abrasive cut.

Inspect the surface under light shining across it at a low angle. This makes stray scratches and orbital sanding marks easier to see. The same guide cautions that veneer is easy to sand through. On veneered plywood or furniture, do not treat a deep scratch as permission to keep removing material.

Sanding between coats is a separate job

Once you have applied a coating, you are working on a thin layer of finish. The aim is usually to remove small surface imperfections and prepare for the next coat, while keeping that layer intact. Wait for the drying interval specified by the manufacturer and sand lightly.

Polyurethane does not have one universal between-coat grit. General Finishes describes using 400-grit paper between several of its topcoats, while Minwax Fast-Drying Polyurethane specifies 220-grit paper. That is why the P320 row is conditional. Follow the exact product's grit and drying instructions, rather than substituting from the chart.

Do not automatically sand the final coat. Very fine abrasives, including P600 and finer, belong to a planned finishing or polishing process. For example, Mirka's high-gloss process uses abrasives as fine as P3000 before polishing. A finish that is dry enough to recoat may not be fully cured. For rubbing out a completed finish, use a method and curing schedule approved for that coating.

What about metals, plastics and wet sanding?

Metals and plastics appear in general grit guides because fine abrasives serve those materials too. They require their own process, however. 3M's Wetordry range includes products intended for clear coats, plastics and metal, with waterproof backing for wet sanding. Ordinary paper is not automatically suitable. Choose an abrasive and procedure approved for the particular surface; there is no universally safe starting grit for every plastic. Wet sanding a coating also needs that coating manufacturer's approval.

Clean the surface before the next step

Vacuum away sanding dust, including dust along edges and joints. Then use the final cleaning method specified for your finish and let the surface dry if required. For example, Rubio's furniture instructions call for vacuuming followed by its Raw Wood Cleaner. Do not assume one solvent or treated cloth suits every coating.

If the project has old paint of unknown composition, stop before dry sanding it. Minwax warns that disturbing old paint can release lead-containing dust. Establish what the coating is and use an appropriate removal method before returning to the sanding sequence.