Magnified schematic — the wire-to-opening ratio is true to scale; very thin lines are drawn at a minimum visible width.
A US standard No. 230 test sieve (ASTM E11) has a nominal opening of 63 µm.
| Opening (microns) | 63 µm |
| Opening (millimeters) | 0.063 mm |
| Opening (inches) | 0.0025 in |
| US standard sieve | No. 230 |
| Tyler equivalent | 250 mesh |
| Pitch (wire center to center) | 108 µm |
| Typical wire diameter | 0.045 mm |
| Approx. open area | 34% |
A 63 µm opening falls within the very fine sand (62.5 µm–125 µm) class of the Wentworth grain-size scale. Comparing grain size with the nominal opening only: silt and finer would pass; fine sand and coarser would be retained; very fine sand is split at about 63 µm. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
These applications commonly use a 230 mesh count or an opening near 63 µm:
110 · 156 · 230 · 305 threads per inch
Screen printing mesh is polyester, counted in threads per inch: 110 and 156 are the common general-purpose counts; 230 and 305 hold finer detail. Not comparable to metal sieve openings.
Ranges show common practice with sources on the mesh size by application page — always check your equipment maker's recommendation.
The name "230 mesh" suggests 230 openings per inch, i.e. a pitch of 25,400 ÷ 230 = 110.4 µm. Standard test sieves, however, are defined by their opening, not by the count: a 63 µm opening woven with the typical 0.045 mm wire gives a real pitch of 63 + 45 = 108 µm, which is about 235.2 wires per inch. That is why mesh numbers and micron values never line up perfectly — and why this site uses the ASTM E11 opening as the answer.
| Mesh | Microns (µm) | Millimeters | Inches |
|---|---|---|---|
| 150 mesh | 106 | 0.106 | 0.0042 |
| 170 mesh | 90 | 0.09 | 0.0035 |
| 200 mesh | 75 | 0.075 | 0.003 |
| 230 mesh | 63 | 0.063 | 0.0025 |
| 250 mesh | 63 | 0.063 | 0.0025 |
| 270 mesh | 53 | 0.053 | 0.0021 |
| 300 mesh | ≈ 51 | 0.051 | 0.002 |
Values are ASTM E11 nominal openings (Tyler equivalents for 150 and 250 mesh). Italic ≈ values are estimates for non-standard mesh counts, calculated from the mesh count and an assumed wire diameter (interpolated between ASTM E11 sieves, or extrapolated beyond No. 635). Wire values are ASTM E11 typical wire for standard sizes.
230 mesh is 63 µm, which is 0.063 mm or 0.0025 inches.
In a simplified comparison with the nominal opening, particles smaller than about 63 µm can pass a 230 mesh screen. A 63 µm opening falls within the very fine sand (62.5 µm–125 µm) class of the Wentworth grain-size scale. Comparing grain size with the nominal opening only: silt and finer would pass; fine sand and coarser would be retained; very fine sand is split at about 63 µm. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
With a typical 0.045 mm wire, 230 mesh has roughly 34% open area. Thicker wire lowers the open area and the opening size.