🕸️ Particle size

Mesh Size Calculator

Convert between mesh numbers, microns, millimetres and inches — for sieves, screens, powders and abrasives. Values between standard sieves are interpolated, and the nearest real sieve is named. Press Calculate.

Written and reviewed by SM Arijul Islam · Last reviewed 29 October 2026 · Editorial standards · Report an error

What a mesh number means

A mesh number is the count of openings in one linear inch of screen. A 100 mesh sieve has 100 openings per inch, so its apertures are roughly 150 micrometres across — a quarter of the width of the wire itself coming out of the count. Bigger mesh number, smaller opening.

The relation is not linear. In a coarse 4 mesh sieve the wires are thick and the openings large, so halving the aperture roughly doubles the mesh number. In a fine 325 mesh sieve the wire takes up most of the inch and the openings shrink much more slowly. That is why the conversion chart is used for exact work and why values between the standard sizes are interpolated logarithmically here rather than by straight-line proportion.

Reading the – and + signs

–100 mesh means the material passes through a 100 mesh sieve: smaller than 150 µm.
+100 mesh means it is retained on that sieve: larger than 150 µm.
100/200 means it passed a 100 mesh and was held on a 200 mesh, so it sits between 75 and 150 µm.

US mesh versus Tyler mesh

Both series describe openings per inch, but the wire diameters differ slightly, so the published mesh numbers drift apart in the middle of the range. A Tyler 150 is close to a US 140, and a Tyler 9 sits with a US 10. Above about 325 mesh the two series agree almost exactly. When a specification names only one, the nearest equivalent below is a safe reading.

Where common mesh sizes turn up

Everyday uses of common mesh sizes
Mesh	Aperture	Common use
4 – 10	4.75 – 2.00 mm	Drainage gravel, coarse sand, aquarium substrate
20 – 40	850 – 425 µm	Soil screening, coffee grinders, spices
60 – 80	250 – 180 µm	Flour sifting, general powders, glazes
100 – 140	150 – 106 µm	Fine flour, cocoa, paint pigment
200 – 325	75 – 45 µm	Pigments, cement, fine ceramic bodies
400 – 635	38 – 20 µm	Sieves for mineral analysis, toners, fine chemicals

Common mesh sizes in microns and millimetres

Common US mesh numbers with their approximate aperture
US mesh	Aperture	Also
10 mesh	2.00 mm	2,000 µm
12 mesh	1.70 mm	1,700 µm
25 mesh	710 µm	0.71 mm
140 mesh	106 µm	0.106 mm
325 mesh	45 µm	0.045 mm

Worked examples

200 mesh is 74 µm, or 0.074 mm — the particle size that defines fine aggregate in concrete.
A 250 µm particle is about 60 mesh, close to the standard flour sieve.
500 mesh is 25 µm, roughly the limit of woven wire cloth before the holes close up.
A powder specified as –325 mesh has particles smaller than 45 µm.

Frequently asked questions

Is mesh the same everywhere?

No. US mesh, Tyler mesh, British Standard and the ISO series all count openings per inch but use different wire diameters, so the apertures differ by a few percent at the same number. Always ask which standard a specification means.

Why does mesh stop around 400?

The wires have to hold the screen together. Past about 500 openings per inch the wires are so fine that the sieve is fragile and the openings are no longer regular, so finer separation moves to air classification or other methods.

Why is the interpolation logarithmic?

Because the sieve series is built as a geometric progression — each standard sieve is roughly a fixed ratio smaller than the one before. Straight-line interpolation between 200 and 230 mesh would be noticeably wrong; log-log lands within a fraction of a micron.

Does mesh describe the average particle?

No, it describes a screen opening. Material that passes a sieve has a maximum size, not an average one: a –100 mesh powder contains everything from 150 µm down to dust.

Common mistakes to avoid

Assuming a bigger mesh number means a bigger particle. It is the reverse.
Converting between mesh series as if they were identical. US and Tyler differ through the middle of the range.
Treating the mesh number as an average particle size instead of a maximum opening.
Ignoring screen loading. A sieve overloaded with powder lets fines through slowly and gives a misleading cut.

Sources and standards

Mesh numbers are not a universal unit. The US series follows ASTM E11, while the ISO and British series use different wire diameters and apertures for the same number, so a 100 mesh sieve is not the same opening in every catalogue. The page names the series in use and gives the aperture in micrometres rather than relying on the number.

Mesh size chart and mesh to micron

Mesh counts the openings per inch of screen, so a higher mesh means a smaller opening. The relationship is roughly mesh to micron: opening µm ≈ 14,900 ÷ mesh, which is close enough for a sanity check but not for a specification — the wire diameter matters, so always use the standard table for the sieve series you are working to.

Mesh size chart with micron and millimetre openings
Mesh	Opening (µm)	Opening (mm)
10 mesh	2,000 µm	2.00 mm
20 mesh	841 µm	0.841 mm
40 mesh	420 µm	0.420 mm
60 mesh	250 µm	0.250 mm
100 mesh	149 µm	0.149 mm
200 mesh	74 µm	0.074 mm
325 mesh	44 µm	0.044 mm
400 mesh	37 µm	0.037 mm
635 mesh	20 µm	0.020 mm

Mesh numbers are not interchangeable between the ASTM and Tyler series, and a “100 mesh” coffee grind is not a 100-mesh sieve opening. Check which standard a supplier means before specifying a mesh size.