Is P120 the same as 120 grit?

Yes, for practical purposes. Through the coarse and medium range, roughly P36 to P220, the FEPA P scale and the North American CAMI scale use the same numbers for nearly the same particle size. P120 averages about 127 microns and CAMI 120 is close enough that no one working wood would see a difference. The two scales only separate above about P240.

Does grit conversion matter for sanding a floor?

Almost never. A floor runs somewhere between 12 and 220 grit from the first cut to the final screen, and the two scales match across that entire range. Buy the number the job calls for and ignore the prefix. Conversion starts to matter in fine finishing work, automotive refinishing, and between-coat sanding above 240.

What does the micron number mean?

It is the average diameter of the abrasive particle. Grit numbers are a grading label, microns are a measurement. A P220 grain averages about 65 microns and a P400 about 35. Micron grading is used directly on film-backed abrasives and lapping films, where the number on the package is the particle size rather than a screen count.

Are published micron figures exact?

No, and they vary a few percent between sources, because the standards define particle size by different methods including sieve analysis, sedimentation and laser diffraction. The figures on this page follow Klingspor published grading data. Treat them as the grading midpoint rather than a tolerance.

Sandpaper Grit Conversion Chart: CAMI, FEPA P, Micron

Q: Where do CAMI and FEPA actually stop matching?

Around P240. Below that the numbers track each other. Above it the P scale keeps subdividing while CAMI does not, so P240 and P280 both land near CAMI 240, P400 lands near CAMI 320, and P600 lands near CAMI 360. At the very fine end the gap is wide, with CAMI 600 sitting roughly where P1200 does.

Q: Which scale does Virginia Abrasives use?

CAMI, like most abrasives sold into the North American flooring and construction trade. European manufacturers such as Mirka and Festool grade to FEPA and print the P prefix. Where a package shows a bare number it is almost always CAMI.

By Matt Lipman · Reviewed by Professional Sandpaper Guide editorial team · Updated August 17, 2026 · NWFA-aligned

Two grading scales cover almost every sheet, disc and belt sold in North America. CAMI is the North American standard and prints a bare number. FEPA is the international standard and prints a P in front of the number. A third label, micron, gives the particle diameter directly and appears mostly on film-backed and lapping abrasives.

The practical answer most people need is short. Through the coarse and medium grits, roughly P36 to P220, the two scales use the same numbers. P80 is 80. P120 is 120. They only pull apart in the fine grits.

Conversion table

FEPA P	CAMI	Average particle size
P36	36	524 microns
P40	40	412 microns
P50	50	326 microns
P60	60	260 microns
P80	80	197 microns
P100	100	156 microns
P120	120	127 microns
P150	150	97 microns
P180	180	78 microns
P220	220	65 microns
P240	240	58.5 microns
P280	240	52.5 microns
P320	280 to 320	46.2 microns
P360	no direct match	40.5 microns
P400	320	35 microns
P500	no direct match	30.2 microns
P600	360	25.75 microns

Micron figures follow Klingspor published grading data, read August 2026. Published values vary a few percent between sources because the standards measure particle size by different methods. Treat them as the grading midpoint.

Where the scales separate, and why

Below about P240 the two systems track each other closely enough that the distinction is academic.

Above it they diverge, and the gap widens as the grit gets finer. The reason is that the P scale keeps subdividing into steps CAMI does not have. P240 and P280 both land near CAMI 240. P400 lands near CAMI 320. By the very fine end the mismatch is large, with CAMI 600 sitting roughly where P1200 does.

The practical rule follows from that. Pick a scale and stay inside it. Substituting a P-graded sheet for a CAMI-graded one at the same printed number is harmless at 80 grit and will change your finish at 400.

For floor sanding, this does not matter

A floor runs from about 12 grit on the first cut to 220 at the finest screen. The two scales match across that entire range, so a floor sanding sequence works the same whichever label is on the package.

The sequence itself is what matters. Our floor sanding grit chart covers the progression pass by pass, and the sheet calculator works out how many of each you need.

Where it does matter

Work	Typical range	Why conversion matters
Automotive refinishing	P400 to P3000	Entirely inside the divergent range. Mixing scales changes the scratch pattern under clear coat.
Between coats of finish	220 to 400	Sits right at the boundary. A P400 sheet cuts noticeably finer than a CAMI 400.
Fine woodworking and instrument work	320 and up	The gap is wide and shows in the surface.
Metal polishing and lapping	micron graded	Sold by particle size directly rather than by grit number.
Floor sanding	12 to 220	Does not matter. The scales agree.
Drywall finishing	100 to 220	Does not matter. See our drywall grit guide.

How to tell which scale you are holding

The prefix is the whole test. A P means FEPA. A bare number means CAMI in almost every case on North American shelves.

Brand is a reasonable second signal. European manufacturers such as Mirka and Festool grade to FEPA. Virginia Abrasives, Norton and 3M sell CAMI into the North American trade. Where a listing gives no prefix and no brand, treat it as CAMI and expect a looser tolerance, because the CAMI standard permits a wider spread of particle sizes inside one grade than the P scale does.

Grit ranges by job

Once the scale question is settled, the useful question is which number to reach for.

Grit	Class	Typical use
12 to 24	Extra coarse	Heavy stock removal, badly cupped or painted floors
36 to 40	Very coarse	First cut on an old finish, heavy leveling
50 to 80	Coarse	Second and third floor passes, shaping
100 to 120	Medium	Final drum pass, general purpose, first drywall pass
150 to 180	Fine	Pre-finish prep, drywall before primer
220 to 320	Very fine	Between coats, bare wood before stain
400 and up	Extra fine	Automotive, polishing, finish build

For the floor-specific version with pass-by-pass detail, see the floor sanding grit chart. For what the abrasive grain is made of and how that changes cut and life, see our guide to aluminum oxide, silicon carbide, ceramic and zirconia.

How much to buy

Grit conversion does not change quantity, but the two questions usually arrive together. For floor work, budget roughly three to four drum sheets per grit for a 500 square foot room across a four-grit sequence, plus one spare per grit. Our sheet calculator does the per-square-foot math including species hardness, and the drum sheet guide covers pack sizes and current pricing.

Matt.