Mesh · Micron · ASTM E11

Mesh to micron converter: ASTM E11 sieve sizes

Write the particle size spec in the sieve your QC lab runs.

Last updated 2026-09-27. Math runs in your browser, no data leaves your computer.

Powder specs arrive as mesh numbers, microns, or inches, often all three on one COA. Look up a numbered sieve, or type a particle size and see which ASTM E11 sieve it falls between.

Use microns to mesh when a supplier quotes a size in µm and your spec or QC lab works in sieve numbers.

The list holds every numbered sieve in ASTM E11, from No. 3½ at 5.6 mm down to No. 635 at 20 µm.

ASTM E11 sieve size chart

Standard openings for the numbered sieves in ASTM E11, with inches converted from the metric opening at exactly 25.4 mm per inch.

Sieve No. Opening (µm) Opening (mm) Opening (in)
No. 3½ 5,600 5.6 0.2205
No. 4 4,750 4.75 0.1870
No. 5 4,000 4 0.1575
No. 6 3,350 3.35 0.1319
No. 7 2,800 2.8 0.1102
No. 8 2,360 2.36 0.0929
No. 10 2,000 2 0.0787
No. 12 1,700 1.7 0.0669
No. 14 1,400 1.4 0.0551
No. 16 1,180 1.18 0.0465
No. 18 1,000 1 0.0394
No. 20 850 0.85 0.0335
No. 25 710 0.71 0.0280
No. 30 600 0.6 0.0236
No. 35 500 0.5 0.0197
No. 40 425 0.425 0.0167
No. 45 355 0.355 0.0140
No. 50 300 0.3 0.0118
No. 60 250 0.25 0.0098
No. 70 212 0.212 0.0083
No. 80 180 0.18 0.0071
No. 100 150 0.15 0.0059
No. 120 125 0.125 0.0049
No. 140 106 0.106 0.0042
No. 170 90 0.09 0.0035
No. 200 75 0.075 0.0030
No. 230 63 0.063 0.0025
No. 270 53 0.053 0.0021
No. 325 45 0.045 0.0018
No. 400 38 0.038 0.0015
No. 450 32 0.032 0.0013
No. 500 25 0.025 0.0010
No. 635 20 0.02 0.0008

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Where the numbers come from

ASTM E11, the standard specification for woven wire test sieve cloth and test sieves, fixes a nominal opening for each sieve and gives the familiar No. designations as alternatives to the metric size. The table on this page is the E11 series as published by Gilson, a test sieve supplier, running from No. 3½ at 5.6 mm to No. 635 at 20 µm.

Inches are converted from the metric opening at 25.4 mm per inch, the exact definition in NIST Handbook 44, and rounded to four decimals. E11 also lists larger sieves designated directly in inches, from 1/4 inch upward, which sit above No. 3½ and are left out here because they are rarely used for chemical powders.

For a size between two sieves, the tool reports the finest sieve the particle still passes and the next finer sieve that would hold it back. Writing both into a spec, for example 100 percent passing No. 270 (53 µm), tells the supplier's lab and yours exactly which cloth to use.

Worked example: minus 325 mesh against a 50 µm sheet

The booking. Your filler spec calls for 100 percent passing 325 mesh, and a new supplier's data sheet says particle size 50 µm maximum. Nobody on the call remembers the exact opening, 50 µm sounds like 325 mesh, and the trial order goes in, which looks fine on paper.

The failure. ASTM E11 puts the No. 325 opening at 45 µm, so every particle between 45 and 50 µm stays on the sieve. Your QC lab runs the standard sieve, the lot shows residue on the cloth, and it fails incoming inspection. The choice is the usual one: accept the coarser powder, or return it.

The fix. Put the spec in both units, 100 percent passing No. 325 (45 µm) per ASTM E11, and send it with the purchase order. If your process can take it, No. 270 at 53 µm matches the supplier's 50 µm grade; if it cannot, the supplier grinds to the finer cut, and the next lot passes on the first test.

Packing the powder into drums or bags on pallets? The drum and IBC palletising calculator works out the pallet and container count at /tools/chemicals/drum-ibc-palletising-calculator.

Checking an impurity limit on the same COA? The concentration converter handles ppm, percent, and mg/L at /tools/chemicals/concentration-converter.

Frequently asked

How many microns is 200 mesh?

A No. 200 sieve under ASTM E11 has a 75 µm opening, which is 0.075 mm or about 0.0030 inch. Anything sold as minus 200 mesh should pass that sieve. The same table puts No. 100 at 150 µm and No. 325 at 45 µm.

Why not just divide 25,400 by the mesh number?

Because the wire takes up part of every inch. Mesh counts wires per inch, and the opening is what is left after the wire takes its share. Two cloths with the same count but different wire diameters have different openings, so ASTM E11 fixes the opening for each numbered sieve instead. That is why the tool uses the standard table rather than dividing 25,400 by the mesh count.

Is a Tyler mesh the same as an ASTM E11 sieve number?

Not always, and a spec should say which series it means. Tyler equivalent mesh is a separate series, and ISO 3310 shares many openings with E11 while adding metric sizes of its own. This tool covers the numbered US standard sieves in ASTM E11 only, and if a supplier quotes Tyler mesh, ask for the opening in µm.

What does passing and retained mean on a particle size spec?

Passing is the share of a sample that falls through a given sieve, and retained is the share left on top. A spec of 99 percent passing No. 100 means at most 1 percent may stay on the 150 µm cloth. Writing the micron opening next to the sieve number, as in No. 100 (150 µm), removes any doubt about which series applies.

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