How this calculator works
The mesh number counts the openings per linear inch of a woven sieve. The actual opening also depends on the wire diameter, so a mesh number does not have a single universal micron value across all standards and wire gauges. The table uses the widely published nominal openings for the standard US sieve series. Treat the result as the expected opening for a standard sieve, and check the sieves certificate when a specification is critical.
Formula
There is no exact conversion from mesh to microns because the wire diameter varies. This page looks up the nominal opening from the standard series instead. For the listed sieves, opening in millimetres = opening in microns / 1,000 and opening in inches = opening in millimetres / 25.4.
Worked example
100 mesh has a nominal opening of 149 microns, 0.149 mm or 0.00587 inches. 200 mesh is 74 microns, and 400 mesh is 37 microns. The smallest opening in the table is 37 microns and the largest is 6,733 microns at 3 mesh.
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Frequently asked questions
Is mesh the same as microns?
No. Mesh counts openings per inch, while a micron is a length of one millionth of a metre. The opening size falls as the mesh number rises, but wire diameter prevents a single exact formula.
Why do mesh charts differ slightly?
Different standards and wire gauges produce different openings for the same mesh count. The values here are the common nominal series; a certificate from the sieve maker is the authority for a particular sieve.
Which way does the size go?
A higher mesh number means more openings per inch and therefore a smaller opening. Going from 100 to 200 mesh roughly halves the nominal opening from 149 to 74 microns.