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. 70 test sieve (ASTM E11) has a nominal opening of 212 µm.
| Opening (microns) | 212 µm |
| Opening (millimeters) | 0.212 mm |
| Opening (inches) | 0.0083 in |
| US standard sieve | No. 70 |
| Tyler equivalent | 65 mesh |
| Pitch (wire center to center) | 352 µm |
| Typical wire diameter | 0.14 mm |
| Approx. open area | 36% |
A 212 µm opening falls within the fine sand (125 µm–250 µm) class of the Wentworth grain-size scale. Comparing grain size with the nominal opening only: very fine sand and finer would pass; medium sand and coarser would be retained; fine sand is split at about 212 µm. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
These applications commonly use a 70 mesh count or an opening near 212 µm:
No. 70 sieve (212 µm) — at least 98% must pass
US standard of identity: at least 98% of "flour" must pass a woven wire cloth no coarser than 212 µm (No. 70). This is a regulatory limit, not the only sieve a mill may use.
Sieves from 200 to 1600 µm
Coffee sifters stack interchangeable sieves between 200 and 1600 µm to isolate a target grind range.
Ranges show common practice with sources on the mesh size by application page — always check your equipment maker's recommendation.
The name "70 mesh" suggests 70 openings per inch, i.e. a pitch of 25,400 ÷ 70 = 362.9 µm. Standard test sieves, however, are defined by their opening, not by the count: a 212 µm opening woven with the typical 0.14 mm wire gives a real pitch of 212 + 140 = 352 µm, which is about 72.2 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 |
|---|---|---|---|
| 45 mesh | 355 | 0.355 | 0.014 |
| 50 mesh | 300 | 0.3 | 0.0118 |
| 60 mesh | 250 | 0.25 | 0.0098 |
| 70 mesh | 212 | 0.212 | 0.0083 |
| 80 mesh | 180 | 0.18 | 0.0071 |
| 100 mesh | 150 | 0.15 | 0.0059 |
| 120 mesh | 125 | 0.125 | 0.0049 |
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.
70 mesh is 212 µm, which is 0.212 mm or 0.0083 inches.
In a simplified comparison with the nominal opening, particles smaller than about 212 µm can pass a 70 mesh screen. A 212 µm opening falls within the fine sand (125 µm–250 µm) class of the Wentworth grain-size scale. Comparing grain size with the nominal opening only: very fine sand and finer would pass; medium sand and coarser would be retained; fine sand is split at about 212 µm. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
With a typical 0.14 mm wire, 70 mesh has roughly 36% open area. Thicker wire lowers the open area and the opening size.