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. 4 test sieve (ASTM E11) has a nominal opening of 4,750 µm.
| Opening (microns) | 4,750 µm |
| Opening (millimeters) | 4.75 mm |
| Opening (inches) | 0.187 in |
| US standard sieve | No. 4 |
| Tyler equivalent | 4 mesh |
| Pitch (wire center to center) | 6,350 µm |
| Typical wire diameter | 1.6 mm |
| Approx. open area | 56% |
A 4,750 µm opening falls within the pebbles (4 mm–64 mm) class of the Wentworth grain-size scale. Comparing grain size with the nominal opening only: granules and finer would pass; pebbles is split at about 4,750 µm. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
These applications commonly use a 4 mesh count or an opening near 4,750 µm:
No. 4, 8, 16, 30, 50, 100 sieves
ASTM C33/C33M-23 grades fine aggregate on the No. 4 to No. 100 sieves: 95–100% passing No. 4 (4.75 mm) and 0–10% passing No. 100 (150 µm).
No. 4 (gravel/sand) · No. 200 (fines)
ASTM D2487 uses the No. 4 sieve (4.75 mm) to separate gravel from sand and the No. 200 sieve (75 µm) to define fines.
Ranges show common practice with sources on the mesh size by application page — always check your equipment maker's recommendation.
The name "4 mesh" suggests 4 openings per inch, i.e. a pitch of 25,400 ÷ 4 = 6,350 µm. Standard test sieves, however, are defined by their opening, not by the count: a 4,750 µm opening woven with the typical 1.6 mm wire gives a real pitch of 4,750 + 1,600 = 6,350 µm, which is about 4 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 |
|---|---|---|---|
| 4 mesh | 4,750 | 4.75 | 0.187 |
| 8 mesh | 2,360 | 2.36 | 0.0929 |
| 10 mesh | 2,000 | 2 | 0.0787 |
| 12 mesh | 1,700 | 1.7 | 0.0669 |
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.
4 mesh is 4,750 µm, which is 4.75 mm or 0.187 inches.
In a simplified comparison with the nominal opening, particles smaller than about 4,750 µm can pass a 4 mesh screen. A 4,750 µm opening falls within the pebbles (4 mm–64 mm) class of the Wentworth grain-size scale. Comparing grain size with the nominal opening only: granules and finer would pass; pebbles is split at about 4,750 µm. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
With a typical 1.6 mm wire, 4 mesh has roughly 56% open area. Thicker wire lowers the open area and the opening size.