What is Sandpaper Grit? Your Complete Guide to Understanding Abrasive Particles

Walking into a hardware store can feel overwhelming, especially when you're faced with the vast array of sandpaper options lining the shelves. With so many varieties to choose from, it's easy to feel lost in the selection.

Interestingly, despite its name, modern sandpaper actually contains neither sand nor paper. Today's abrasive tools are sophisticated products featuring cloth or paper backing coated with precisely sized particles like aluminum oxide, silicon carbide, or ceramic materials—a far cry from the crude tools of the past.

Understanding sandpaper grit helps you get good, professional results when you work on a project. If you're refinishing furniture, preparing it for paint, or smoothing metal, selecting the right sandpaper grit is crucial. The right choice can help you get a nice finish or save you from working too long. 

Sandpaper Grit Explained

Sandpaper grit is the size of the abrasive particles attached to the back of the sandpaper. You can think of these particles like small cutting tools. Each of them helps remove some of the material from your project when you sand it. The grit rating is a numerical value that indicates the size of each abrasive particle, and here's where it gets counterintuitive: lower numbers mean larger, coarser particles, while higher numbers indicate smaller, finer particles.

For example, 40-grit sandpaper feels rough because it has big abrasive particles. On the other hand, 400-grit sandpaper feels smooth when you touch it. This is because it is made up of very tiny abrasive particles.

How is Sandpaper Grit Measured?

The way we measure grit is both interesting and exact. People determine grit by counting the number of abrasive particles that pass through a mesh screen. This screen covers one square inch. Manufacturers use special sifting tools. This equipment sorts the abrasive particles by size. They do this by using several filters, with each one getting a bit finer.

Picture dropping basketballs and marbles through the same hoop. You can fit many more marbles, which are like fine grit, through the hoop than you can with basketballs, which are like coarse grit. The number of particles in one square inch is called the grit number.

This system is in place to maintain consistency across different companies. A 120-grit sandpaper from one brand will work about the same as a 120-grit from any other. This helps you know what to get when looking for grit sandpaper, no matter who makes it.

Related Article: The Ultimate Guide on How to Measure a Sanding Belt

Understanding Different Grit Categories

Extra Coarse Grit (24-36)

These strong grits take on the hardest jobs. You can use them for:

• Removing several coats of paint

• Taking off old varnish from wood floors

• Shaping heavy areas and getting rid of lots of material

• Doing rough first steps on surfaces that are very damaged

Caution: These grits can take off a lot of material fast. If you are not careful, they might damage your workpiece.

Coarse Grit (40-80)

Perfect for heavy-duty sanding tasks:

• Take off the old paint and the finish

• Smooth out rough lumber

• Round over any sharp edges

• Do the first sanding of reclaimed wood

• Remove rust from metal surfaces

Medium Grit (100-150)

This is your main range. It is good for many uses and does not need perfect care.

• You can use this for sanding most kinds of materials.

• It helps smooth a surface after you finish coarse sanding.

• This can get the bare wood ready for its finish.

• It is also good for taking off light paint.

• Most home improvement work starts and ends with this step.

Pro Tip: 150-grit is good if you want to paint a surface. It leaves the right feel for the paint to stick well.

Fine Grit (180-220)

Use these for detailed finishing work:

• Do the last sanding step before you put stain on bare wood.

• Make the surface smooth between each coat of finish.

• Give a light scratch to painted places before you paint again.

• Get the surfaces ready if you want a good finish.

Important: Do not sand bare wood that you plan to stain with anything rougher than 220-grit sandpaper. If you use coarser sandpaper, you will see scratch marks on your finished project.

Extra Fine Grit (240-400)

These grits work really well for polishing and getting a finish that is very smooth:

• Sanding between several finish coats

• Getting surfaces ready for shiny, high-gloss finishes

• Wet sanding in car work

• Making painted surfaces feel smooth

Ultra Fine Grit (500+)

Reserved for specialized applications, such as:

• Mirror-finish polishing

• Jewelry making

• Optical lens finishing

• High-end automotive detailing

Types of Abrasive Materials

The type of abrasive material you use has a big effect on how well it works.

Aluminum oxide is one of the most valuable choices for sanding. You can use it on wood, metal, and plastic. As you use them, the bits of aluminum oxide wear down, revealing new, sharp sides. This helps the sandpaper last longer and keeps it working well.

Silicon carbide is a good choice for wet sanding and for sanding harder materials. It works faster than aluminum oxide. However, it does not last as long as aluminum oxide.

Ceramic is a top choice that can last up to six times longer than other normal abrasives. It is good for power sanding jobs.

Zirconia Alumina is very tough and long-lasting. It is best suited for large jobs on wood, metal, and fiberglass. You can achieve good results with it because it performs well on challenging tasks and continues to work effectively.

Related Article: Best Sanding Belts for Woodworking: Aluminum Oxide vs. Zirconia

Choosing the Right Grit: A Strategic Approach

To work effectively with sandpaper, you need to know how to transition from rough to smooth. Here is the key rule: start the work with the roughest grit that will get the job done fast. After that, move on to the next smoother grit. Keep going to finer grits until you get the smooth feel you want.

Pro Tips for Better Results

When working with sandpaper, matching your tools to the grit you're using makes a significant difference in your results. Power sanders work exceptionally well with coarser grits, helping you remove material quickly and efficiently. However, as you progress to finer grits, hand sanding often provides better control and more consistent results across the surface.

Don't forget to check your progress as you work through different grits. Taking the time to thoroughly wipe down your work surface each time you switch grit levels reveals any remaining scratches from the previous stage. This simple habit ensures you don't move forward until the surface is properly prepared for the next step.

Quality truly matters when it comes to sandpaper selection. While premium sandpaper requires a higher upfront investment, it typically outlasts cheaper alternatives and delivers noticeably better results. The improved cutting action and durability often make the extra cost worthwhile, especially on important projects.

Finally, proper storage extends the life of your sandpaper significantly. Keep your sandpaper in a dry location away from moisture, which can damage the backing material and reduce the adhesive bond holding the abrasive particles. A simple storage solution can save you money and ensure your sandpaper performs when you need it.

Cost Considerations

Sandpaper is one of the most affordable things you can have in the workshop. Most of the time, you will pay from $2 to $25 for it. This depends on how many you buy, what size you get, and how good the sandpaper is. If you buy multi-packs, you usually get better value for your money. Getting packs that come with different grits also helps make sure you are ready for any project.

Think about the cost for the whole project, not just the cost for each sheet. Premium sandpaper lasts longer and often gives better value than cheaper options that wear out fast. This way, you can get more out of your money and finish your work better, too.

Mastering the Art of Grit Selection

Understanding sandpaper grit helps you move from just picking up any sandpaper to being someone who picks the best one for the job. When you choose sandpaper grit, think about the material you have. You also need to know what you want from your project and what tools you will be using. The right choice can make your work much better.

No matter if you are someone who likes to do small jobs around the house on weekends or you work as a craftsperson, learning how to pick the right grit can help you. It will make your work better and also help you go faster. Start by learning these basics, and you will soon know which sandpaper to use in every situation without much thought.

The key is to practice and watch closely. Pay attention to how different grits work on your project. When you do this, you will get better and soon have the skills to get professional-quality results every time.