What Do The Numbers On Sandpaper Mean? | Grit Guide Now

The Big Idea Behind Grit Numbers

Every sheet, disc, or sponge carries a number that tells you how large the abrasive particles are. Low numbers cut fast and leave deep scratches. High numbers cut gently and leave shallow scratches. Two naming systems appear on packaging: a P prefix points to the FEPA scale used for coated abrasives, while plain numbers usually follow the ANSI/CAMI scale used in North America. Both describe size ranges, not a single exact grain.

If you see P80, you’re on the FEPA track. If you see 80 without a letter, you’re likely on the ANSI/CAMI track. FEPA also uses F for bonded stones and D/B for diamond or cBN, but coated papers carry the P mark. You can read about those designations on the FEPA standards page, which explains the families and what each prefix means.

Because grit is a range, two sheets with the same label can still feel different across brands. That’s normal. Both must land inside the tolerance window defined by the standard, yet the distribution inside that window can vary.

What Do The Numbers On Sandpaper Mean For Your Project

Think in terms of scratch depth and next step. Pick a starting number that removes the current defect in a controllable way, then step through grits to erase the previous scratch. Jumping too far leaves ghost lines. Crawling through every single grit wastes time. A two-to-three step rise tends to hit the sweet spot for most jobs.

Use the table below as a working map. It blends common FEPA P values with typical tasks and approximate median particle sizes. Actual tolerances span a band; brands can land at different points inside that band.

When in doubt, test on a scrap piece. Start higher than you think, drop one step if the defects linger, then climb in measured steps once the surface evens out.

Sandpaper Number Meaning And Grit Scale Basics

FEPA and ANSI/CAMI describe grain size in different ways. FEPA’s coated-abrasive P grades are built around particle-size distributions measured by sedimentation and screening. ANSI/CAMI ties many sizes to screen openings and also assigns distributions for fine ranges. You can scan a friendly overview in UAMA’s abrasives 101.

The result on your bench is simple: P80 and 80 live in the same neighborhood, while high numbers drift apart more. That’s why P1000 does not match 1000 on a polishing film. Numbers at the far end of either scale step into microgrit territory and no longer map to simple mesh counts.

Because brands can set their blend within a tolerance band, feel can shift. A premium sheet may pack a tighter curve around the median, which gives a cleaner scratch pattern and faster follow-up steps.

Reading The Label Like A Pro

Look For The “P”

A clear P before the number signals FEPA grading for coated papers. No letter usually means ANSI/CAMI. Stones or wheels often carry an F grade. Diamond films may show a micron value instead of a grit number. FEPA’s overview of families spells this out on their standards page.

Check Mineral Type

Aluminum oxide suits wood, paint, plastics, and mild steel. Silicon carbide cuts hard and sharp on glass, stone, and finishes, and it loves water. Zirconia lives on belts for stainless and aggressive stock removal. Ceramic grains stay sharp for a long time and shine in high-pressure work. Mineral choice controls speed and wear, while the number controls scratch depth.

Backings And Weight Codes

Paper weights run from light A to heavy F. Cloth backings run J through Y and up. Light paper conforms to curves; heavy paper stays flat and steady. Film backings deliver a dead-even scratch in fine ranges and resist tearing. Pick the backing for the job, not just the grit.

Open Coat Vs Closed Coat

Open coat leaves gaps between grains so dust can escape; it helps on soft woods and paints that clog. Closed coat packs grains edge to edge for a fast, even cut on hard surfaces. The number stays the same; the feel changes.

Wet Or Dry

Wet-dry sheets control loading and cool the surface. Use light strokes, refresh water often, and wipe the slurry before jumping to the next grit. This is standard practice in auto finishing; 3M’s sanding guide outlines the sequences and tool tips that keep swirls at bay (3M Random Orbital Sanding Guide).

Microns, Meshes, And Why “1000” Isn’t Always The Same

Below about P240, many grades still trace back to screen openings per inch, which makes the number easy to picture. Above that, both scales rely on measured particle size in microns and on how a batch spreads around its median. This is why a P2000 sheet and a “1000” polishing film can behave differently. The labels anchor to different standards and measurement methods, so treat the digits as a map, not a promise of identical feel.

When mixing brands or swapping between P and non-P labels, test two close options side by side. Pick the one that erases the previous scratch in the fewest strokes without leaving fresh tracks of its own.

Smart Grit Progressions That Save Time

Here’s a compact set of sequences that work across common materials. Each line shows a practical starting point and two or three follow-ups that clear the scratch in predictable steps. Jump sizes reflect how stubborn the material is and how visible the scratch will be under finish or light.

On large panels, keep your pattern consistent and finish each step before you reach for the next grit. A random-orbital with fresh discs speeds this up and keeps the scratch uniform. Start and stop off the work to avoid blooms and boomerang marks, a tip shared in the 3M guide.

Choosing The Right Form Factor

Sheets And Blocks

Full sheets cut into thirds drop neatly into a standard sanding block. A firm cork or rubber block stays flat and helps you hold a straight edge. Foam blocks conform to curves and mouldings without cutting through high spots.

Discs And Hook-And-Loop Pads

Stick-on and hook-and-loop discs come in the full grit spread and remove material quickly. Use a pad that matches the job: soft for contours, firm for flats. Pair dust extraction with net or multi-hole discs to keep the surface cool and clean.

Belts

Belts shine on shaping and heavy removal. Choose zirconia or ceramic for metals and tough hardwoods. Keep tracking straight, clear dust often, and relax pressure as you climb in grit.

Sponges And Pads

Sponges carry fewer numbers and more feel. Fine, medium, and coarse labels map roughly to P240–P600 ranges. Use sponges for profile work, scuffing between coats, and spot touchups where a block would leave flats.

Small Moves That Improve Results

Use A Pencil Guide

Lightly cross-hatch the surface with a pencil before each step. Sand until the marks vanish evenly. This keeps you honest about coverage and helps avoid shiny low spots that reappear under finish.

Match The Pad To The Stage

Hard pads leave crisp, flat results on panels. Soft pads help on edges and contours. Many random-orbit systems list pad hardness by color or code; keep one of each in your kit.

Keep Dust Out Of The Scratch

Dust packs into scratches and dulls the next grit. Vacuum and wipe between steps, even on bare wood. On wet work, wipe the slurry with a clean cloth before moving on.

Replace Abrasive Sooner

Fresh paper cuts cool and clean. If the sheet looks glazed or loads seconds after you start, switch. Your finish will thank you, and the next grit will work faster.

Common Traps With Grit Numbers

Jumping Too Far

P80 to P320 looks efficient on paper, yet P320 won’t erase deep P80 tracks in a reasonable window. Step through P120 or P150 first to set a scratch size the higher grit can clear.

Stopping Too High On Bare Wood

Very high grits can burnish fibers and block stain. On tight-grain hardwoods, P150 or P180 often gives richer color than P220. On soft woods, P220 calms fuzz while still taking stain well.

Expecting “1000” To Be Universal

A “1000” on a polishing film and a P1000 on paper live in different systems. Treat the label as a clue, test on a corner, and pick by scratch quality rather than the printed number alone.

Ignoring Mineral And Backing

A P220 silicon carbide sheet and a P220 aluminum oxide sheet won’t feel the same on clear coat. Backing, coating density, and grain toughness steer the experience even when the number matches.

When To Choose Micron-Rated Sheets

In the ultra-fine range, many film sheets and discs list micron sizes instead of grit. Micron labels speak directly to particle size and are handy for predictable polishing sequences. If your work depends on tight control—like buff-ready panels or plastic optics—micron steps give a tidy ladder. Learn the context first with a standard chart, then build a small set that matches your compound and pad system.

Care, Storage, And Shelf Life

Store sheets flat in a dry bin. Keep discs in sleeves or a binder so the hooks stay clean. Heat and humidity can curl paper and weaken bonds, which leads to uneven scratch patterns. If a sheet sheds grains on the first swipe, toss it. Life is cheap compared with a rework.

Trusted Standards And Where To Learn More

If you want the definitions straight from the groups that write them, scan the FEPA grains overview and UAMA’s Abrasives 101. For hands-on technique with random-orbit tools and fine-grit workflows, the 3M Random Orbital Sanding Guide is a solid companion.

Once you know what the numbers signal and how the scales differ, sanding turns into a planned series of small steps. Choose a start that fits the defect, climb in steady gaps, and let the final finish show the care in each pass.