Sandpaper Grit Converter
Convert sandpaper grit numbers to micron particle size.
Look up CAMI and FEPA grit equivalents for woodworking and finishing.
Select a grit number — see the micron size and typical use.
Sandpaper grit numbers indicate the size of abrasive particles.
Higher grit = finer abrasive = smoother finish.
Common grit to micron conversions (CAMI standard):
| Grit | Microns | Use |
|---|---|---|
| 40 | 425 | Heavy material removal |
| 60 | 268 | Rough shaping |
| 80 | 190 | Initial sanding |
| 100 | 140 | General sanding |
| 120 | 115 | Smoothing before finish |
| 150 | 92 | Final sanding before paint |
| 180 | 78 | Between coats |
| 220 | 68 | Fine finish sanding |
| 320 | 46 | Very fine sanding |
| 400 | 35 | Wet sanding |
| 600 | 25 | Ultra fine, polishing |
| 1000 | 18 | Mirror finish |
| 2000 | 10 | Final polish |
Approximate formula:
- Microns = 25,400 / grit (rough approximation)
- Actual values vary by standard (CAMI vs FEPA/P-grade).
The two standards exist because the US (CAMI) and Europe (FEPA) developed grit scales independently. They track closely in the coarse grades but drift apart at the fine end, so a “400 grit” CAMI paper and a “P400” FEPA paper aren’t identical. The “P” prefix is the quick way to spot a FEPA grade, and when precision matters the micron size is the only truly unambiguous measure, since it’s the actual particle diameter rather than a scale number.
The grit number itself is roughly the count of abrasive particles per inch, so higher means finer. The practical rule when sanding is not to skip grits: jumping from 80 straight to 220 leaves scratches the finer paper can’t erase. Step through the sequence (say 80, 120, 180, 220) and let each grade remove the marks left by the last, and the final surface comes out clean. Patience through the grades beats brute force every time.
How we build and check this converter
This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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