Sandpaper Grit Calculator for mixed brands of paper. Convert a CAMI grit to its P-grade match by particle size, check a jump from your last grit, and test a whole sanding sequence.
A P before the number means FEPA P-grade. No P usually means the US CAMI scale.
Check a Grit Jump
Enter the grit you sanded with last. It can be on a different scale.
Check Your Grit Sequence
List grits in the order you sand. Add P for P-grades and µm for micron sizes.
Grit Steps From Here
| Grit | Average | Size Drop | From Here |
|---|---|---|---|
| 120 Grit | 116 µm | - | Coarser |
| 150 Grit | 93 µm | - | Coarser |
| 180 Grit | 78 µm | - | Your grit |
| 220 Grit | 66 µm | 1.18× | Next grade |
| 240 Grit | 53.5 µm | 1.46× | Skips one, OK |
| 280 Grit | 44 µm | 1.77× | Too big a jump |
| 320 Grit | 36 µm | 2.17× | Too big a jump |
| 360 Grit | 28.8 µm | 2.71× | Too big a jump |
| 400 Grit | 23.6 µm | 3.31× | Too big a jump |
CAMI and P-Grade Size Chart
| CAMI | P-Grade | Average |
|---|---|---|
| P24 | 764 µm | |
| 24 | 715 µm | |
| P30 | 642 µm | |
| 30 | 638 µm | |
| P36 | 538 µm | |
| 36 | 535 µm | |
| 40 | 428 µm | |
| P40 | 425 µm | |
| 50 | 351 µm | |
| P50 | 336 µm | |
| P60 | 269 µm | |
| 60 | 268 µm | |
| P80 | 201 µm | |
| 80 | 192 µm | |
| P100 | 162 µm | |
| 100 | 141 µm | |
| P120 | 125 µm | |
| 120 | 116 µm | |
| P150 | 100 µm | |
| 150 | 93 µm | |
| P180 | 82 µm | |
| 180 | 78 µm | |
| P220 | 68 µm | |
| 220 | 66 µm | |
| P240 | 58.5 µm | |
| 240 | 53.5 µm | |
| P280 | 52.2 µm | |
| P320 | 46.2 µm | |
| 280 | 44 µm | |
| P360 | 40.5 µm | |
| 320 | 36 µm | |
| P400 | 35 µm | |
| P500 | 30.2 µm | |
| 360 | 28.8 µm | |
| P600 | 25.8 µm | |
| 400 | 23.6 µm | |
| P800 | 21.8 µm | |
| 500 | 19.7 µm | |
| P1000 | 18.3 µm | |
| 600 | 16 µm | |
| P1200 | 15.3 µm | |
| P1500 | 12.6 µm | |
| 800 | 12.3 µm | |
| P2000 | 10.3 µm | |
| 1000 | 9.5 µm | |
| P2500 | 8.4 µm | |
| 1200 | 6.5 µm |
Matching Grits With the Sandpaper Grit Calculator
The Sandpaper Grit Calculator converts a grit between the US CAMI scale and the European P-grade scale by comparing real particle size. It also checks whether a jump from your last paper is too big, and whether a full grit sequence skips too many grades.
It is for woodworkers whose shop drawer holds a mix of brands, and for anyone following a finishing schedule written for one scale while holding paper marked in the other. It also covers the finishing grades past sandpaper, such as A-grade pads, Micro-Mesh and lapping film.
Why 600 Grit and P600 Are Not the Same Paper
A grit number on its own does not tell you the size of the abrasive. Klingspor explains that a P in front of the number marks the FEPA scale used across Europe, while paper without a P is usually graded to the US CAMI scale. The P is printed on the back of the sheet.
Up to about 220, the two scales track closely. Past that point they split, and the same number on a P sheet means larger grains. The table uses Klingspor's average particle sizes for CAMI grades and the FEPA values listed by Sizes.com for P-grades.
| Number on the paper | CAMI average | P-grade average | P sheet is coarser by |
|---|---|---|---|
| 180 | 78 µm | 82 µm | 5% |
| 220 | 66 µm | 68 µm | 3% |
| 240 | 53.5 µm | 58.5 µm | 9% |
| 320 | 36 µm | 46.2 µm | 28% |
| 400 | 23.6 µm | 35 µm | 48% |
| 600 | 16 µm | 25.8 µm | 61% |
| 1000 | 9.5 µm | 18.3 µm | 93% |
| 1200 | 6.5 µm | 15.3 µm | 135% |
By 1200, a P sheet carries grains more than twice the size of CAMI paper with the same number. That is why CAMI 600 matches P1200, and why a finishing schedule that says 400 without a P is asking for something close to P600.
The two scales are not even measured the same way. Sizes.com notes that FEPA defines each grade by a range of grain sizes, while CAMI sets an average size, so any match between them is a closest fit rather than an exact equal.
How the Sandpaper Grit Calculator Finds the Closest Match
Each grade in the calculator carries its average particle size in microns. To find the match, it looks for the grade on the other scale whose size is closest by ratio, not by plain difference.
Comparing by ratio treats a 10 µm gap between coarse grits as small and the same gap between fine grits as large, which is how the scratches behave. The hero then shows how far the match is from your paper as a percentage.
For CAMI 180 at 78 µm, the closest P-grade is P180 at 82 µm, which is 5% coarser. You can also type a size in microns, as printed on lapping film and some polishing papers, and the tool returns the nearest sandpaper grade.
Grits run from above 0 up to 20,000. A number that is not a standard grade, such as 170, snaps to the closest listed grade with a note. Anything well outside the charts, or a micron size under 4.5 or over 800, gets a warning that the match is rough.
Checking a Grit Sequence Against the One-Skip Rule
3M prints the rule on its Pro Grade Precision sanding tools. It says to work from coarse to fine and not to skip more than one grit between sanding steps. Each paper has to remove the scratches of the one before it, and a paper too far down the scale cannot reach them.
The calculator lays your list against the grade ladder of the finer paper and counts the grades between each pair. One skipped grade passes, two turns the step red, and the Grits to Add row names what to insert. A step that goes coarser, or repeats the same size under two names, is flagged too.
The default sequence of 80, 120, 180 and 220 passes. Its biggest step, 80 to 120, drops from 192 to 116 µm, a ratio of about 1.66 with only 100 skipped. Going straight from 80 to 150 would skip both 100 and 120, and the tool asks for 120 in between.
Because every grade is compared by size, a list that mixes scales still works. Type P in front of P-grades and µm after micron sizes, and a P400 after CAMI 320 is judged by its real grains, not its number.
The rule is a guideline, and woodworkers apply it differently. A LumberJocks member quotes Bob Flexner's Understanding Wood Finishing as saying not to skip a grit when hand sanding, but that skipping one is fine with a power sander. The Sanding Schedule Calculator builds a full sequence from your starting surface and adds time and discs to buy.
Going Past Sandpaper With Finishing Grades
The third card maps your grit onto three finishing systems. Klingspor's chart places A-grades, the finishing scale on structured pads like 3M Trizact, alongside CAMI and P-grades, so A110 sits with 180 grit at 78 µm and A16 with P1200 at 15.3 µm.
Micro-Mesh uses its own numbers. Its maker, Micro-Surface, says 1500 Micro-Mesh leaves a scratch pattern like 400 wet or dry paper, and its conversion chart puts 1500 at 30 µm with grades running to 12000. Lapping film is sold by micron size directly, and the tool matches films from 100 µm down to 1 µm.
Turners often switch to these grades on the lathe, where sanding speed matters as much as grit. The Lathe Speed Calculator covers the slower spindle speed JET suggests for sanding bowls.
Mix-Ups That Leave Scratches Behind
Reading a P-grade as CAMI is the most common one. A mixed pack sorted by the printed number can put P400 after CAMI 400, which is a step back to larger grains, and the tool flags that order.
Treating a micron number as a grit is the second. A 30 µm film disc is close to P500, not 30 grit, so choose Micron Size as the scale before typing it.
The third is sanding bare wood far past what the finish needs. Sizes.com notes that many workers see 180 as fine enough for raw wood under varnish or lacquer, with finer grades saved for between coats.
Grit Questions Woodworkers Ask
Is P1200 the same as 1200 grit?
No, and the gap is large. P1200 averages 15.3 µm, which matches CAMI 600 at 16 µm, while CAMI 1200 averages 6.5 µm. That makes plain 1200 grit paper less than half the grain size of P1200.
If a finishing schedule was written in the US and names 1200 grit without a P, the closest standard P-grade is P2500 at 8.4 µm. Check the back of each sheet before you follow a schedule across brands.
Can I skip grits when sanding wood?
You can skip one grade but not two, according to 3M's guidance. Going 80 to 120 skips 100 and is fine, while 80 to 150 skips both 100 and 120 and leaves scratches the finer paper cannot reach.
Many woodworkers are stricter by hand. Flexner, as quoted on LumberJocks, advises using every grit when hand sanding and allows one skip with a power sander. Enter your list in the sequence check and the tool counts the skipped grades for you.
What grit should I stop at before finishing bare wood?
For film finishes like varnish or lacquer, Sizes.com notes that many woodworkers stop at 180 on bare wood. On CAMI paper that is 78 µm, and the matching P-grade is P180 at 82 µm, so either scale works at this stage.
The finer grades still have a job between coats and for sanding grain that a stain raised. Sizes.com lists 320 as the coarsest grade used for that step.
Where does Micro-Mesh fit in a sanding sequence?
Micro-Surface puts 1500 Micro-Mesh at about the scratch of 400 wet or dry paper, around 30 µm. Its wood instructions say to start at 1500 once the regular sandpaper scratches are gone and work through each grade to 12000.
For finish coats, Micro-Surface suggests sanding from 1500 to 3200 or 3600 between coats. After the last coat cures, polishing starts at 2400 and goes up through the finer pads.