Wire Mesh Size Chart: Mesh to Micron & mm

Last reviewed on October 3, 2026

This chart converts wire mesh count to opening size (aperture) in millimetres, inches and microns for common stainless steel woven wire cloth, from 2 mesh to 635 mesh. Because the opening depends on wire diameter as well as mesh count, each row lists the wire diameter it assumes. If your mesh uses a different wire, use the calculator below.

The Formula

For square-weave cloth (plain or twill):

Example: 30 mesh with 0.30 mm wire → 25.4 ÷ 30 = 0.847 mm pitch, minus 0.30 mm = 0.547 mm (547 µm) opening, and (0.547 ÷ 0.847)² = 42% open area.

Mesh Aperture Calculator

Enter a mesh count and wire diameter.

Mesh to Micron Chart

Wire diameters are typical market combinations for each count, rounded; your supplier may offer others. Apertures are calculated nominal values — woven cloth has manufacturing tolerances, defined for industrial wire cloth in ISO 9044.

Mesh Wire (in) Wire (mm) Opening (in) Opening (mm) Opening (µm) Open Area
2 0.0630 1.600 0.4370 11.10 11,100 76%
4 0.0470 1.194 0.2030 5.16 5,156 66%
5 0.0410 1.041 0.1590 4.04 4,039 63%
8 0.0280 0.711 0.0970 2.46 2,464 60%
10 0.0250 0.635 0.0750 1.91 1,905 56%
12 0.0230 0.584 0.0603 1.53 1,532 52%
14 0.0200 0.508 0.0514 1.31 1,306 52%
16 0.0180 0.457 0.0445 1.13 1,130 51%
18 0.0170 0.432 0.0386 0.979 979 48%
20 0.0160 0.406 0.0340 0.864 864 46%
24 0.0140 0.356 0.0277 0.703 703 44%
30 0.0120 0.305 0.0213 0.542 542 41%
40 0.0100 0.254 0.0150 0.381 381 36%
50 0.0090 0.229 0.0110 0.279 279 30%
60 0.0075 0.190 0.0092 0.233 233 30%
80 0.0055 0.140 0.0070 0.178 178 31%
100 0.0045 0.114 0.0055 0.140 140 30%
120 0.0037 0.094 0.0046 0.118 118 31%
150 0.0026 0.066 0.0041 0.103 103 37%
200 0.0021 0.053 0.0029 0.074 74 34%
250 0.0016 0.041 0.0024 0.061 61 36%
325 0.0014 0.036 0.0017 0.043 43 30%
400 0.0010 0.025 0.0015 0.038 38 36%
500 0.0010 0.025 0.0010 0.025 25 25%
635 0.0008 0.020 0.0008 0.020 20 24%

Which Mesh Size for Which Job?

Test Sieve Numbers Are Not Mesh Counts

Laboratory test sieves are designated by number (ASTM E11) or by aperture (ISO 3310-1), and the number refers to a standard aperture, not to a wire count you can verify by counting. That is why charts based on sieves list "No. 100 = 150 µm" while industrial 100 mesh cloth with 0.0045″ wire has about 140 µm openings. Standard sieve apertures:

ASTM E11 Sieve Nominal Aperture
No. 4 4.75 mm
No. 8 2.36 mm
No. 10 2.00 mm
No. 16 1.18 mm
No. 20 850 µm
No. 30 600 µm
No. 40 425 µm
No. 50 300 µm
No. 60 250 µm
No. 80 180 µm
No. 100 150 µm
No. 120 125 µm
No. 140 106 µm
No. 200 75 µm
No. 230 63 µm
No. 270 53 µm
No. 325 45 µm
No. 400 38 µm

Rectangular and Dutch Weave Mesh

For rectangular mesh such as 18 × 16, work out each direction separately: with 0.011″ wire, 18 mesh gives 1/18 − 0.011 = 0.0446″ (1.13 mm) and 16 mesh gives 0.0515″ (1.31 mm). Dutch weaves (for example 24 × 110) have no straight-through square opening, so the formula does not apply; use the manufacturer's tested micron rating instead.

Frequently Asked Questions

How do I convert mesh to microns?

Divide 25,400 by the mesh count to get the wire pitch in microns, then subtract the wire diameter in microns. For 100 mesh with 0.114 mm (114 µm) wire: 25,400 ÷ 100 = 254 µm, minus 114 µm = 140 µm.

Is 100 mesh always 150 microns?

No. 150 µm is the aperture of a standard No. 100 test sieve. Industrial 100 mesh cloth is defined by wire count, and its opening depends on the wire: with the common 0.0045 inch wire it is about 140 µm, with heavier wire it is smaller.

What does 18 x 16 mesh mean?

The cloth has 18 wires per inch in one direction and 16 in the other, so the openings are rectangular. It is a common insect-screen specification. Calculate each direction separately with the same formula.

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