Mastering Sandpaper Grit Ratings: A Guide to the Perfect Finish
The choice of sandpaper grit is often the make-or-break element in achieving a rough, amateurish finish or a perfect, professional result when preparing timber, metal or paint surfaces. Whether you are a seasoned tradesperson or a dedicated DIY enthusiast, it is important to know how to work with the grit scale. This knowledge will help you save time and achieve the best results possible.
What Exactly Is “Grit”?
Simply put, “grit” is how many abrasive particles are in a square inch of sandpaper. The lower the grit number the larger and coarser the particles. The higher the grit number, the smaller and finer the particles. If you know the grit to use and in what order you will prevent accidental damage to your workpiece and avoid wasting time trying to remove paint with sandpaper that is too fine.
The Sandpaper Grit Scale Explained
| Grade | Grit Range | Primary Use | Example |
| Extremely Coarse | 12 – 36 | Stripping thick paint, heavy rust, and severe imperfections | Garryson GARABEC Garryflex Abrasive Block – Extra Coarse 36 Grit (Pink) |
| Coarse | 40 – 60 | Rapid material removal, levelling, and rough shaping | Faithfull 60G Aluminium Oxide Sanding Roll |
| Medium | 80 – 120 | Smoothing bare timber and removing coarse scratches | Faithfull 120G Aluminium Oxide Sanding Roll |
| Fine | 150 – 240 | Final surface preparation before applying paint or varnish | Draper 03156 Sanding Discs, 125mm, Hook & Loop, 240G (10 Pack) |
| Very Fine | 320 – 400 | Lightly scuffing between topcoats and wet sanding | Faithfull FAIARS115320 Silicon Carbide Finishing Sanding Roll, 115 mm x 5 m, 320 g |
| Ultra Fine | 600 – 1000+ | Polishing automotive bodywork and glass-like finishes | Sealey WD23281000 Wet & Dry Paper 230 x 280 mm, 1000 Grit |
1. Coarse (40 to 60 Grit)
- Best for: Heavy material removal, stripping old paint or varnish, and shaping rough timber.
- The Details: Coarse grit is aggressive. It is designed to tear through material quickly but will leave noticeable scratches on the surface. You should never use it for final finishing.
- Top Pick from Toolden: Faithfull FAIAR560R Aluminium Oxide Sanding Paper Roll (60G). This heavy-duty roll is brilliant for demanding applications where durability and rapid material removal are a priority.
2. Medium (80 to 120 Grit)
- Best for: Smoothing out rough patches, removing minor imperfections, and preparing surfaces for their first coat of primer or stain.
- The Details: Once you have shaped your wood with coarse paper, a medium grit will help level out the deep scratches left behind. 120 grit is often the go-to starting point for standard woodwork.
- Top Pick from Toolden: Faithfull FAIAR5120R Aluminium Oxide Sanding Paper Roll (120G). Featuring a robust E-weight backing, this roll is perfect for efficient smoothing and blending on both wood and metal.
3. Fine (150 to 240 Grit)
- Best for: Final surface preparation before applying a finish or sanding between coats of paint or varnish.
- The Details: Fine grit creates a beautifully smooth surface, ensuring that your final coats of paint or lacquer look pristine.
4. Very Fine to Ultra Fine (320 to 600+ Grit)
- Best for: Polishing, wet sanding, and achieving a glass-like finish on bespoke furniture or automotive bodywork.
- The Details: These grits are strictly for the finishing touches, lightly scuffing the surface to ensure maximum adhesion for your final topcoat without leaving any visible marks.
The Golden Rule: Move Up the Grades. The biggest mistake you can make is skipping too many grades at once. If you start with a 40-grit, do not jump straight to a 240-grit. The finer paper simply will not be able to remove the deep grooves left by the coarse abrasive. Instead, work your way through the scale sequentially (for example, moving from 60 to 80 to 120 and finally 240). This methodical approach saves effort and guarantees a superior finish.
Why is the abrasive backing material important?
The backing material of your abrasive is just as important as the grit itself. Selecting the wrong backing can lead to the paper tearing too soon or the abrasive wearing out before you finish the job. Here’s how the three main types of backing compare:
Here is how the three main backing types compare:
- Paper Backing: The most common and affordable option is categorised by weight, ranging from ‘A-weight’ (very light and flexible, ideal for hand-sanding contours) to ‘E-weight’ or ‘F-weight’ (heavy and stiff, perfect for machine sanding flat surfaces). This type of sandpaper is excellent for standard woodworking, but it may tear under heavy mechanical stress.
- Cloth Backing: This material is exceptionally durable and resistant to tearing. Its cloth backing is designed for heavy-duty use and is commonly used in sanding belts for belt sanders or flap discs for angle grinders. It can flex and bend without breaking, making it the preferred choice for metalworking and aggressive timber shaping.
- Film Backing: This finishing option is made from plastic or polyester film and is considered premium quality. It is completely waterproof, making it ideal for wet sanding. Additionally, it offers a perfectly flat surface for the abrasive particles, which helps prevent deep, stray scratches. This ensures a highly uniform and flawless finish, whether on automotive bodywork or high-gloss furniture.
Tips on preventing sandpaper from clogging
There’s nothing more frustrating than putting on a new sanding disc and having it be useless after 30 seconds because it is gummed up with old paint. This clogging is often called “corning”. What happens is this: the friction heats the paint or varnish up, softens it, and makes it sticky, until it sticks to the abrasive surface.
Here’s how to avoid it and get a lot more life out of your abrasives:
1. Switch to Open-Coat Sandpaper
Normal sandpaper is “closed-coat”, and this means that 100% of the surface is covered with abrasive grit. You need an open coat sandpaper to strip the paint and resin. This sort exposes some 30 to 40 per cent of the backing. These microscopic holes permit dust and flakes of paint to pass through, decreasing the chances of the paper getting clogged up to a great extent.
2. Let the Tool Do the Work
If you push hard on your sander or run it at its highest speed, you’ll create extra friction. That heat melts the paint or varnish into the grit. Ease up on the speed dial on your orbital sander and let the abrasive do the work, not you pushing the sander against the surface.
3. Keep an Abrasive Cleaning Stick Handy
If your paper gets clogged, you don’t have to throw it away. Crepe rubber cleaning blocks are the sandpaper’s big rubber.
Just turn on your sander and hold the rubber block against the spinning pad for a couple of seconds. The friction grabs the built-up paint and pulls it right out of the grit, making the disc look almost new.
4. Strip the Heavy Stuff First
If the paint or varnish is very thick, sandpaper is the wrong tool to begin with. First, use a scraper or a chemical paint stripper and a heat gun to remove most of the heavy coating. When you’re down to the bare timber (or just a very thin layer of stubborn primer), go to a coarse (40G-60G) open-coat sandpaper to finish preparation.
Learn a few sanding tricks on our Elevate Your DIY Game: 5 Power Sander Tricks for Smoother Surfaces blog post.
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