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Answer
How to Convert Mesh Count to Opening Size
Quick answer
Mesh count is the number of openings per linear inch. To get the aperture, divide 25.4 mm by the mesh count for the pitch, then subtract the wire diameter: opening = (25.4 / mesh count) - wire diameter (mm). Multiply by 1000 for microns. You must know the wire diameter, because two meshes at the same count but different wires have different openings.
By the WireMeshQA editorial team · Independent wire mesh reference
Mesh count tells you how many openings fall in one linear inch (25.4 mm), but most specifications and filtration jobs need the actual opening size in millimetres or microns. Converting between the two takes one simple formula plus the wire diameter.
The mesh-count-to-opening formula
To find the opening, first work out the pitch (centre-to-centre spacing) from the mesh count, then subtract the wire diameter. Multiply by 1,000 to express the result in microns:
Figure summary: Mesh count is the number of openings per inch; the opening (aperture) is the pitch minus the wire diameter, and pitch (mm) = 25.4 / mesh count. Knowing the mesh count and wire diameter lets you calculate the opening in mm or microns.
You cannot convert mesh count to opening size without the wire diameter — two meshes with the same count but different wire will have different openings.
A worked example
Take 100 mesh with 0.10 mm wire. Pitch = 25.4 / 100 = 0.254 mm. Opening = 0.254 − 0.10 = 0.154 mm, or 154 microns. Change the wire to 0.12 mm and the opening drops to 0.134 mm — which is exactly why the wire diameter always matters.
Mesh count to opening size chart
The table below lists common mesh counts with a typical wire diameter, the resulting pitch, the opening in millimetres and microns, and the open area. Treat the openings as typical values — your exact opening depends on the wire your supplier actually uses.
Mesh count
Typical wire (mm)
Pitch (mm)
Opening (mm)
Opening (micron)
Open area
10
0.90
2.540
1.640
1640
~42%
20
0.50
1.270
0.770
770
~37%
40
0.28
0.635
0.355
355
~31%
60
0.18
0.423
0.243
243
~33%
100
0.10
0.254
0.154
154
~37%
200
0.05
0.127
0.077
77
~37%
Note
Open area (the percentage of the mesh that is holes) drives flow and visibility. For the same mesh count, thinner wire gives a larger opening and a higher open area.
Does a higher mesh count mean finer or coarser?
A higher mesh count means more, smaller openings per inch, so the mesh is finer. 20 mesh is coarse with openings near 0.8 mm, while 200 mesh is fine at roughly 75 microns. As the count climbs, both the opening and the usable wire diameter shrink.
Millimetres, microns and inches
One millimetre equals 1,000 microns, and one inch equals 25.4 mm. So a 0.154 mm opening is 154 microns; a 325 mesh screen with 0.036 mm wire opens to about 0.043 mm, or 43 microns — close to the finest particle the unaided eye can resolve.
Frequently asked questions
What is the formula to convert mesh count to opening size?
Opening (mm) = (25.4 / mesh count) - wire diameter (mm). Divide 25.4 by the mesh count to get the pitch, subtract the wire diameter, then multiply by 1000 for microns.
Do I need the wire diameter to find the opening?
Yes. Mesh count alone fixes the pitch but not the aperture. Two cloths at the same mesh count have different openings if their wire diameters differ, so the wire diameter is essential.
How do I convert millimetres to microns?
Multiply the opening in millimetres by 1000. For example, a 0.355 mm opening equals 355 microns. To go the other way, divide microns by 1000 to get millimetres.
What does 100 mesh mean in microns?
It depends on the wire diameter. With a typical 0.10 mm wire, 100 mesh gives an opening of about 0.154 mm, or roughly 154 microns. A thicker wire would yield a smaller micron rating.
Is higher mesh count finer or coarser?
Higher mesh count is finer. More openings per inch means each opening is smaller, so 200 mesh has a much smaller aperture than 20 mesh assuming comparable wire diameters.
Need to define the specification?
Use the selector to turn the application, opening, wire and material requirements into a clearer mesh brief.