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. 140 test sieve (ASTM E11) has a nominal opening of 106 µm.
| Opening (microns) | 106 µm |
| Opening (millimeters) | 0.106 mm |
| Opening (inches) | 0.0042 in |
| US standard sieve | No. 140 |
| Tyler equivalent | 150 mesh |
| Pitch (wire center to center) | 177 µm |
| Typical wire diameter | 0.071 mm |
| Approx. open area | 36% |
A 106 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 106 µm. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
These applications commonly use a 140 mesh count or an opening near 106 µm:
60 mesh (254 µm) · 100 (152 µm) · 140 (104 µm)
Replacement screens are offered at 60 mesh (254 µm) and finer options such as 100 mesh (152 µm) and 140 mesh (104 µm); pick the coarsest screen that catches your sediment, since finer screens clog faster.
Ranges show common practice with sources on the mesh size by application page — always check your equipment maker's recommendation.
The name "140 mesh" suggests 140 openings per inch, i.e. a pitch of 25,400 ÷ 140 = 181.4 µm. Standard test sieves, however, are defined by their opening, not by the count: a 106 µm opening woven with the typical 0.071 mm wire gives a real pitch of 106 + 71 = 177 µm, which is about 143.5 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 |
|---|---|---|---|
| 80 mesh | 180 | 0.18 | 0.0071 |
| 100 mesh | 150 | 0.15 | 0.0059 |
| 120 mesh | 125 | 0.125 | 0.0049 |
| 140 mesh | 106 | 0.106 | 0.0042 |
| 150 mesh | 106 | 0.106 | 0.0042 |
| 170 mesh | 90 | 0.09 | 0.0035 |
| 200 mesh | 75 | 0.075 | 0.003 |
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.
140 mesh is 106 µm, which is 0.106 mm or 0.0042 inches.
In a simplified comparison with the nominal opening, particles smaller than about 106 µm can pass a 140 mesh screen. A 106 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 106 µm. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
With a typical 0.071 mm wire, 140 mesh has roughly 36% open area. Thicker wire lowers the open area and the opening size.