A Complete Guide to Sandpaper Grit Classification

The sandpaper grit refers to the size of the abrasive materials on the sandpaper. Various standards exist to ascertain sandpaper grit size. Common standards include the CAMI or Coated Abrasive Manufacturers Institute and the FEPA or Federation of European Producers of Abrasives. The lower the number of the sandpaper grit, the coarser the grit grade will be.

Macro Grits

The sandpaper grit at the macro grit levels range across the following sub-types:

Extra Coarse: These are very coarse types of sandpaper grit and ensure expedited removal of all kinds of material as well as the initial sanding on hardwood flooring. As per the FEPA standards, the sandpaper grit sizing is denoted by P30, P36, P12, P16 etc, while the CAMI standards denote the classes as 24, 30 or 36. The average diameter of the sandpaper grit particles can range anywhere between 530 to 1815 micrometers.

Coarse: These types of sandpaper grit classes ensure rapid material removal. As per FEPA standards, these are classified as P40 or P50 and as per CAMI standards, are denoted as 40, 50 or 60. The typical diameter of the sandpaper grit ranges between 336 to 425 micrometers.

Medium: These kinds of sandpaper grit are used to sand bare wood to prepare it for varnish removal or final finishing. The FEPA standards denote such types of sandpaper grit by P60 or P80 and CAMI standards denote it as 80. The diameter of the particles ranges between 190 to 265 micrometers.

Fine: These kinds of sandpaper grit are used to prepare wood for the finishing. Such sandpaper grit types are not suited for varnish removal or removing paint on wood. These can also be used to clean plaster as well as water stains present on wood. The FEPA standards denote such sandpaper grit types as P100 or P120 while CAMI standards denote them as 100 and 120. The diameter size of the particles ranges between 115 and 162 micrometers.

Very Fine: These kinds of sandpaper grit are used for sanding over bare wood. As per FEPA standards, such sandpaper grit are denoted by P150, P180, P220 while CAMI standards denote them as 150, 180 or 220. The diameter of the particles ranges between 66 to 100 micrometers.

Micro Grits

The micro grit types of sandpaper grit are classified as follows:

Very Fine: Used for sanding finishes in between consecutive coats. FEPA classifications are P240, P280, P320 or P360 while CAMI classifications are denoted as 240. The diameter size is between 40.5 to 58.5 micrometers.

Extra Fine: Used to initiate wood polishing. FEPA standards classify these types of sandpaper grit as P400, P500 or P600 while CAMI classifies them as 360 or 320 and diameter sizes range between 25.8 to 36.0 micrometers.

Super Fine: Used to sand final finish on the wood. FEPA classifies them as P800, P1000 or P1200 while CAMI classifies them as 400, 500 or 600 and average diameter sizes range from 15.3 to 23.0 micrometers.

Ultra Fine: Used for polishing thick finishes and performing final sanding. FEPA classifies them as P1500, P2000 or P2500 while CAMI classifies these as 800 or 1000 and average diameter size of particles ranges between 8.4 to 12.6 micrometers.

One thing to ensure when using sandpaper is that the bond between sandpaper grit and backing material is not separated during usage.