Mesh to Micron Converter: Sieve Mesh Number to Opening Size (ASTM E11 and Tyler) and Back

How it works

Opening (µm) from the ASTM E11 or Tyler table · mm = µm ÷ 1,000 · inches = µm ÷ 25,400 · Wire cloth: opening = 25.4 mm ÷ mesh count − wire diameter · Open area = (opening ÷ pitch)² × 100% · Mesh numbers between standard sieves: log-log interpolation between neighbours

A sieve’s mesh number tells you roughly how many wires cross one inch of the screen, so a higher number means finer openings. The opening itself is what matters for particle size, and it is always smaller than 25,400 ÷ mesh microns because part of each inch is taken up by wire. That is why test sieves are specified by table, not by formula. The US Standard series in ASTM E11 runs from No. 3½ (5.60 mm) to No. 635 (20 µm) and uses the same openings as the international ISO 565 / ISO 3310-1 series, where each size is about the fourth root of 2 (1.19 ×) larger than the next. The older Tyler series is built on 200 mesh = 74 µm and steps by the same ratio, but its numbers do not match the US ones: US No. 10 (2.00 mm) corresponds to Tyler 9 mesh, and Tyler 10 mesh is 1.65 mm. Use Mesh → microns to look up an opening, Microns → mesh to find which sieve a particle passes or is retained on (for powders, sand, abrasives, food and filtration), or Wire cloth to work out the opening and open area of any square-weave screen from its mesh count and wire diameter. Off-table mesh numbers are estimated by log interpolation between neighbouring sieves and clearly marked. The Wentworth class tells you where the size sits on the sedimentology scale (silt, fine sand, coarse sand…). This page is about sieves and particle size; the screen-printing mesh count calculator covers ink deposit, and the welded wire mesh calculator covers reinforcing mesh for concrete.

Worked example

A No. 200 US Standard sieve has a nominal opening of 75 µm, which is 0.075 mm or 0.0030 in (75 ÷ 25,400). Its Tyler equivalent is 200 mesh at 74 µm, its ISO designation is 75 µm, and 75 µm falls in the very fine sand class. As a cross-check, 25,400 ÷ 200 = 127 µm is the pitch of opening plus wire, so the wire is about 52 µm thick.

Sources: Endecotts / CAL Laboratory: American Standard sieve series ASTM E11 (designations and openings) · AGM Container Controls: Mesh equivalents (US sieve to Tyler mesh) · 911 Metallurgist: Mesh to micron conversion table (Tyler 200 mesh = 0.074 mm basis, √2 series) · ConductScience: Mesh to micron converter (325 mesh = 45 µm example)

Frequently asked questions