40 Mesh to Micron – Opening Size in µm & mm
40 mesh ≈ 420 µm
A US standard 40 mesh sieve has openings of about 420 µm (0.42 mm, 0.0165 in).
Step by step
- Mesh 40 means about 40 openings per linear inch.
- Opening size depends on wire thickness, so it is read from the standard sieve series (ASTM E11).
- 40 mesh ≈ 420 µm.
40 mesh separates medium to fine sand, flour-sized particles and many powders.
Details
- Opening
- 420 µm
- Millimeters
- 0.42 mm
- Inches
- 0.0165 in
- Compared with a human hair (~70 µm)
- 6×
How it works
Mesh number counts the openings per linear inch of a woven screen. Because the wire takes up space, the opening is smaller than 25.4 mm divided by the mesh count, and different wire gauges give different openings — so standard sieve series fix the exact opening for each number. Values here follow the US standard series; Tyler mesh numbers are close but not identical.
Nearby values
Related conversions
Frequently asked questions
What is 40 mesh in microns?
About 420 µm.
What is 40 mesh in mm?
0.42 mm.
Is higher mesh finer?
Yes — more openings per inch means smaller openings.
What is the difference between US and Tyler mesh?
They are two standard series with nearly the same openings; the numbers differ slightly for some sizes.