01 — StandardWhat is 400 mesh in microns?
A US standard No. 400 test sieve (ASTM E11) has a nominal opening of 38 µm.
02 — Specifications400 mesh specifications
| Opening (microns) | 38 µm |
| Opening (millimeters) | 0.038 mm |
| Opening (inches) | 0.0015 in |
| US standard sieve | No. 400 |
| Tyler equivalent | 400 mesh |
| Pitch (wire center to center) | 68 µm |
| Typical wire diameter | 0.03 mm |
| Approx. open area | 31% |
03 — ApplicationsWhat is 400 mesh used for?
A 38 µm opening falls within the silt (3.9 µm–62.5 µm) class of the Wentworth grain-size scale. Comparing grain size with the nominal opening only: very fine sand and coarser would be retained; silt is split at about 38 µm. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
We have no sourced application data for openings this size yet.
Ranges show common practice with sources on the mesh size by application page — always check your equipment maker's recommendation.
04 — CalculationHow the 400 mesh value is calculated
The name "400 mesh" suggests 400 openings per inch, i.e. a pitch of 25,400 ÷ 400 = 63.5 µm. Standard test sieves, however, are defined by their opening, not by the count: a 38 µm opening woven with the typical 0.03 mm wire gives a real pitch of 38 + 30 = 68 µm, which is about 373.5 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.
05 — CompareNearby mesh sizes
| Mesh | Microns (µm) | Millimeters | Inches |
|---|---|---|---|
| 270 mesh | 53 | 0.053 | 0.0021 |
| 300 mesh | ≈ 51 | 0.051 | 0.002 |
| 325 mesh | 45 | 0.045 | 0.0018 |
| 400 mesh | 38 | 0.038 | 0.0015 |
| 450 mesh | 32 | 0.032 | 0.0013 |
| 500 mesh | 25 | 0.025 | 0.001 |
| 600 mesh | ≈ 21.2 | 0.021 | 0.0008 |
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.
06 — FAQFrequently asked questions
How many microns is 400 mesh?
400 mesh is 38 µm, which is 0.038 mm or 0.0015 inches.
What size particles pass through a 400 mesh screen?
In a simplified comparison with the nominal opening, particles smaller than about 38 µm can pass a 400 mesh screen. A 38 µm opening falls within the silt (3.9 µm–62.5 µm) class of the Wentworth grain-size scale. Comparing grain size with the nominal opening only: very fine sand and coarser would be retained; silt is split at about 38 µm. Real sieving also depends on particle shape, sieving time and the opening tolerance of the cloth.
What is the open area of 400 mesh?
With a typical 0.03 mm wire, 400 mesh has roughly 31% open area. Thicker wire lowers the open area and the opening size.