Sandpaper is one of those humble materials that can make or break a woodworking project. Get it right, and your timber feels silky-smooth, takes a finish beautifully, and looks professionally made. Get it wrong, and you'll spend hours chasing scratches, or worse, ruin the surface you've worked so hard to shape. If you're new to DIY and woodworking, the sheer range of grit numbers on the shelves can be baffling. This guide will walk you through the basics of choosing the right sandpaper for any job, so you can sand with confidence.

Why Grit Ratings Matter (and What They Actually Mean)

The grit number on a sheet of sandpaper tells you how many abrasive particles are packed into each square inch. The lower the number, the coarser the paper. A P40 grit is very aggressive and will strip material away quickly, but it leaves deep scratches. A P240 grit is much finer, removing very little material but leaving a smooth surface. In the UK, most sandpaper uses the P-grade system (also called FEPA), so you'll see numbers like P80, P120, P180 and so on. The jump between grades matters: as a rule of thumb, never skip more than one grade at a time. Going from P80 straight to P180 will leave scratches that are difficult to remove. Instead, step through P80, P120 and then P180.

Here's a quick breakdown of the main categories:

• Coarse (P40–P80): for shaping timber, removing old paint or varnish, and levelling rough-sawn boards.
• Medium (P80–P120): for smoothing out planer marks and preparing the surface for finer sanding.
• Fine (P150–P220): for the final smoothing pass before applying a finish.
• Very fine (P240–P400+): for sanding between coats of varnish or paint, and for delicate work on veneers.

The Three Stages of Sanding a Timber Project

Think of sanding as a process, not a single step. For most bare timber projects, you'll work through three stages: coarse, medium and fine. Start with a coarse grit only if the wood is rough, has deep scratches, or you need to remove an old finish. If the surface is already fairly smooth, you might begin at P120. The key is to remove the scratches left by the previous grit before moving on. So after sanding with P80, switch to P120 and sand until the P80 scratches are gone. Then move to P180, and finally P220 for a finish-ready surface. Always sand with the grain – running your paper across the grain leaves scratches that show up dramatically under a finish. Wrap your paper around a cork or rubber sanding block to keep the surface flat and avoid rounding over edges.

Matching Grit to the Job: Practical Examples

Different projects call for different starting points. Here are some common scenarios you might encounter in a UK workshop or garage:

• Stripping old paint or varnish: start with P60 or P80. Once the old finish is gone, step up to P120 and P180.
• Levelling a hardwood board: begin with P80 to remove any high spots, then P120, then P180.
• Preparing bare wood for stain: sand to P120, then P180. Stop there – going finer can close the grain and prevent the stain from absorbing evenly.
• Final sanding before varnish or oil: use P220. For a really smooth finish, follow with P320.
• Sanding between coats of finish: use P320 or P400. Light pressure only – you're just knocking back dust nibs.
• Sanding end grain: end grain absorbs finish differently and can look blotchy. Go one grit finer than you would on the face grain, and sand lightly.

Hand Sanding vs. Power Sanders

Both have their place. Hand sanding gives you control, which is essential for mouldings, corners and small details. A simple sanding block with a sheet of P120 or P180 will handle most beginner projects. Power sanders, on the other hand, save time on large flat surfaces. A random orbital sander is the best all-rounder for beginners – it's forgiving and leaves a swirl-free finish if you keep it moving. Belt sanders are aggressive and can gouge wood in seconds, so they're best left for stripping large areas. Detail sanders reach into corners. Whatever you use, let the tool do the work. Pressing down hard clogs the paper, generates heat and creates uneven surfaces. Keep the sander moving, and use the correct grit for the stage you're at.

Five Common Sanding Mistakes to Avoid

Even experienced woodworkers make these mistakes from time to time. Avoid them and your finish will be noticeably better:

• Skipping grits. Jumping from P80 to P180 leaves deep scratches. Always step through the grades.
• Sanding across the grain. This leaves visible cross-grain scratches that are almost impossible to hide. Sand along the grain whenever possible.
• Pressing too hard. Extra pressure doesn't speed things up – it just clogs the paper and rounds over edges. Let the abrasive do the work.
• Not removing dust between grits. Coarse particles left on the surface will contaminate your finer paper and scratch the wood. Wipe or vacuum between every grit change.
• Using worn-out paper. If the paper feels smooth, shiny or clogged, it's done. A fresh sheet is cheaper than ruining your project.

With a little practice, choosing the right sandpaper becomes second nature. Start coarse if you need to, work through the grades, and finish fine. Your timber will thank you with a surface that's a joy to touch and a finish that lasts for years.