Mesh to Micron Converter
Convert sieve mesh numbers to microns and back, using the US standard sieve series.
US standard sieve series (ASTM E11)
| Mesh | Microns | mm | Inches |
|---|---|---|---|
| 4 | 4750 µm | 4.75 mm | 0.18701 in |
| 5 | 4000 µm | 4 mm | 0.15748 in |
| 6 | 3350 µm | 3.35 mm | 0.13189 in |
| 7 | 2800 µm | 2.8 mm | 0.11024 in |
| 8 | 2360 µm | 2.36 mm | 0.09291 in |
| 10 | 2000 µm | 2 mm | 0.07874 in |
| 12 | 1700 µm | 1.7 mm | 0.06693 in |
| 14 | 1400 µm | 1.4 mm | 0.05512 in |
| 16 | 1180 µm | 1.18 mm | 0.04646 in |
| 18 | 1000 µm | 1 mm | 0.03937 in |
| 20 | 850 µm | 0.85 mm | 0.03346 in |
| 25 | 710 µm | 0.71 mm | 0.02795 in |
| 30 | 600 µm | 0.6 mm | 0.02362 in |
| 35 | 500 µm | 0.5 mm | 0.01969 in |
| 40 | 425 µm | 0.425 mm | 0.01673 in |
| 45 | 355 µm | 0.355 mm | 0.01398 in |
| 50 | 300 µm | 0.3 mm | 0.01181 in |
| 60 | 250 µm | 0.25 mm | 0.00984 in |
| 70 | 212 µm | 0.212 mm | 0.00835 in |
| 80 | 180 µm | 0.18 mm | 0.00709 in |
| 100 | 150 µm | 0.15 mm | 0.00591 in |
| 120 | 125 µm | 0.125 mm | 0.00492 in |
| 140 | 106 µm | 0.106 mm | 0.00417 in |
| 170 | 90 µm | 0.09 mm | 0.00354 in |
| 200 | 75 µm | 0.075 mm | 0.00295 in |
| 230 | 63 µm | 0.063 mm | 0.00248 in |
| 270 | 53 µm | 0.053 mm | 0.00209 in |
| 325 | 45 µm | 0.045 mm | 0.00177 in |
| 400 | 38 µm | 0.038 mm | 0.0015 in |
| 450 | 32 µm | 0.032 mm | 0.00126 in |
| 500 | 25 µm | 0.025 mm | 0.00098 in |
| 635 | 20 µm | 0.02 mm | 0.00079 in |
Mesh is a count, not a size
A mesh number is how many openings there are per linear inch of screen. So higher mesh means smaller particles pass — the opposite of most size scales. 100 mesh is 150 µm; 400 mesh is 38 µm.
Crucially, mesh alone does not fix the opening. The aperture is the pitch minus the wire thickness:
opening = (25,400 ÷ mesh) − wire diameter, in µm
Two screens both called 100 mesh can have different apertures if they use different wire. That is why standards exist, and why a conversion table beats a formula.
Which standard
The table above is the US standard sieve series, ASTM E11 — the most widely quoted. Tyler mesh differs slightly, and British (BS 410) and ISO series use aperture sizes directly rather than mesh numbers, which sidesteps the ambiguity altogether. Modern specifications increasingly quote microns for exactly that reason.
A sense of scale
A human hair is roughly 70 µm across, about 200 mesh. Fine table salt is around 300 µm (50 mesh), flour about 150 µm (100 mesh), and cement roughly 45 µm (325 mesh). Below about 635 mesh, sieving stops being practical and particle size is measured by other means.
Off-series mesh numbers are interpolated here and flagged as such. For specification work, use the published aperture for the exact screen you have.