Heads up: on the older Tyler scale, 35 mesh means 425 µm (equal to ASTM No. 40). If a spec just says "35 mesh", confirm which standard it uses.
On the older Tyler scale, 35 mesh = 425 µm. Check which standard your spec uses.
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. 35 test sieve (ASTM E11) has a nominal opening of 500 µm.
| Opening (microns) | 500 µm |
| Opening (millimeters) | 0.5 mm |
| Opening (inches) | 0.0197 in |
| US standard sieve | No. 35 |
| Tyler equivalent | 32 mesh |
| Pitch (wire center to center) | 815 µm |
| Typical wire diameter | 0.315 mm |
| Approx. open area | 38% |
A 500 µm opening sits exactly on the Wentworth boundary between medium sand and coarse sand. Comparing grain size with the nominal opening only: grains up to and including 500 µm would pass; grains larger than 500 µm would be retained. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
These applications commonly use a 35 mesh count or an opening near 500 µm:
Water 20–40 mesh · steam 40–60 mesh
A common recommendation: 20–40 mesh for chilled and city water lines, 40–60 mesh for steam (very fine mesh is eroded by high-velocity steam). Follow the equipment maker for your service.
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 "35 mesh" suggests 35 openings per inch, i.e. a pitch of 25,400 ÷ 35 = 725.7 µm. Standard test sieves, however, are defined by their opening, not by the count: a 500 µm opening woven with the typical 0.315 mm wire gives a real pitch of 500 + 315 = 815 µm, which is about 31.2 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 |
|---|---|---|---|
| 20 mesh | 850 | 0.85 | 0.0335 |
| 25 mesh | 710 | 0.71 | 0.028 |
| 30 mesh | 600 | 0.6 | 0.0236 |
| 35 mesh | 500 | 0.5 | 0.0197 |
| 40 mesh | 425 | 0.425 | 0.0167 |
| 45 mesh | 355 | 0.355 | 0.014 |
| 50 mesh | 300 | 0.3 | 0.0118 |
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.
35 mesh is 500 µm, which is 0.5 mm or 0.0197 inches.
In a simplified comparison with the nominal opening, particles smaller than about 500 µm can pass a 35 mesh screen. A 500 µm opening sits exactly on the Wentworth boundary between medium sand and coarse sand. Comparing grain size with the nominal opening only: grains up to and including 500 µm would pass; grains larger than 500 µm would be retained. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
With a typical 0.315 mm wire, 35 mesh has roughly 38% open area. Thicker wire lowers the open area and the opening size.
Those charts use the older Tyler scale, where 35 mesh corresponds to 425 µm (ASTM No. 40). In the US standard (ASTM E11) series, No. 35 is 500 µm.