Particle size analysis · Reference chart
Mesh to Micron Conversion Chart
3–140 mesh, with ASTM E11 cross-reference and conflict notes.
Why a mesh number is not an aperture
This mesh to micron conversion chart exists because a mesh number is a weaving density, not a measurement. It counts the openings per linear inch of woven wire, so the same number can name apertures up to 150 µm apart depending on the series the wire was woven to — and both screens can be described honestly. Every mesh to micron size below is therefore stated as a nominal aperture in millimetres or micrometres; the mesh number is carried only as a shop-floor label.
Columns 4 and 5 cross-reference the ASTM E11 woven-wire test sieve series — the system most aggregate, cement, soil and powder specifications are written against. Of the 21 grades below, 12 cannot be matched to ASTM E11 by number at all: 9 carry the same number as an E11 sieve but a different aperture, and 3 have no E11 equivalent. Wherever the two disagree, trust the aperture.
The chart
Consolidated from the published LVDALAB sieve series (3–140 mesh). Higher mesh number = smaller aperture = finer retention. Rows shaded red share a sieve number with ASTM E11 but not its aperture.
| Mesh (nominal) | Aperture mm | Aperture µm | ASTM E11 sieve no. | ASTM E11 aperture µm | Cross-check |
|---|---|---|---|---|---|
| 3 | 8.000 | 8000 | — | — | not in E11 |
| 4 | 4.750 | 4750 | No.4 | 4750 | identical |
| 6 | 3.500 | 3500 | No.6 | 3350 | +150 µm |
| 8 | 2.500 | 2500 | No.8 | 2360 | +140 µm |
| 10 | 2.000 | 2000 | No.10 | 2000 | identical |
| 12 | 1.700 | 1700 | No.12 | 1700 | identical |
| 14 | 1.430 | 1430 | No.14 | 1400 | +30 µm |
| 16 | 1.180 | 1180 | No.16 | 1180 | identical |
| 18 | 1.000 | 1000 | No.18 | 1000 | identical |
| 20 | 0.900 | 900 | No.20 | 850 | +50 µm |
| 24 | 0.800 | 800 | — | — | not in E11 |
| 30 | 0.600 | 600 | No.30 | 600 | identical |
| 40 | 0.450 | 450 | No.40 | 425 | +25 µm |
| 50 | 0.355 | 355 | No.50 | 300 | +55 µm |
| 60 | 0.300 | 300 | No.60 | 250 | +50 µm |
| 70 | 0.250 | 250 | No.70 | 212 | +38 µm |
| 80 | 0.200 | 200 | No.80 | 180 | +20 µm |
| 100 | 0.150 | 150 | No.100 | 150 | identical |
| 120 | 0.125 | 125 | No.120 | 125 | identical |
| 132 | 0.115 | 115 | — | — | not in E11 |
| 140 | 0.106 | 106 | No.140 | 106 | identical |
Reading the cross-check column. identical — the mesh grade and the ASTM E11 sieve of the same number specify the same aperture. +n µm — the number matches an ASTM E11 sieve, but this grade is n µm coarser. not in E11 — no ASTM E11 sieve carries this number. Totals: 9 identical · 9 same number, different aperture · 3 no E11 equivalent.
Conflict notes
- No. 50 is the expensive one. ASTM E11 No. 50 is 300 µm. The 50-mesh grade in the chart above is 355 µm — which ASTM calls No. 45. A laboratory that orders “50” and receives a 355 µm screen has ordered correctly by one system and received a coarser screen by the other. This single pair accounts for most disputes in aggregate and cement testing.
- The offsets run one way. Every conflicting grade above is coarser than the ASTM E11 sieve of the same number — from +20 µm at 80 mesh up to +150 µm at 6 mesh. The 6, 8, 14, 20, 40, 50, 60, 70 and 80 mesh grades all sit on the coarse side of their ASTM namesakes. Where the two systems agree — No. 4, 10, 12, 16, 18, 30, 100, 120 and 140 mesh — they agree exactly.
- 24 mesh and 132 mesh are not ASTM E11 designations. Neither number appears in the standard series. If a specification calls for them by number, ask for the aperture instead: 800 µm and 115 µm respectively.
- 3 mesh is a label, not a number. An 8.00 mm aperture does exist in ASTM E11 (as 5/16 in), but E11 stops numbering sieves at No. 4 and switches to millimetres or inches above it.
- ISO 3310-1 is a third series again. If a drawing names ISO rather than ASTM, the R20/3 aperture values differ from both columns above. Match on the aperture value in µm in every case.
ASTM E11 woven-wire test sieve series
The full standard series from No. 4 to No. 635. In ASTM E11 the aperture is the specification and the sieve number is the alternative label — not the reverse. Coarser than No. 4 the series is designated in millimetres or inches only, because there is no practical mesh number for it.
| No. | µm | mm |
|---|---|---|
| No.4 | 4750 | 4.750 |
| No.5 | 4000 | 4.000 |
| No.6 | 3350 | 3.350 |
| No.7 | 2800 | 2.800 |
| No.8 | 2360 | 2.360 |
| No.10 | 2000 | 2.000 |
| No.12 | 1700 | 1.700 |
| No.14 | 1400 | 1.400 |
| No.16 | 1180 | 1.180 |
| No.18 | 1000 | 1.000 |
| No.20 | 850 | 0.850 |
| No.25 | 710 | 0.710 |
| No.30 | 600 | 0.600 |
| No.35 | 500 | 0.500 |
| No.40 | 425 | 0.425 |
| No.45 | 355 | 0.355 |
| No. | µm | mm |
|---|---|---|
| No.50 | 300 | 0.300 |
| No.60 | 250 | 0.250 |
| No.70 | 212 | 0.212 |
| No.80 | 180 | 0.180 |
| No.100 | 150 | 0.150 |
| No.120 | 125 | 0.125 |
| No.140 | 106 | 0.106 |
| No.170 | 90 | 0.090 |
| No.200 | 75 | 0.075 |
| No.230 | 63 | 0.063 |
| No.270 | 53 | 0.053 |
| No.325 | 45 | 0.045 |
| No.400 | 38 | 0.038 |
| No.500 | 25 | 0.025 |
| No.635 | 20 | 0.020 |
Coarse and aggregate sizes (ASTM C136)
The sieves called out by ASTM C136 for aggregate grading, where the inch designations and the No. designations meet.
| Sieve | Aperture | Also written |
|---|---|---|
| 1 in | 25.000 mm | 25000 µm |
| 3/4 in | 19.000 mm | 19000 µm |
| 1/2 in | 12.500 mm | 12500 µm |
| 3/8 in | 9.500 mm | 9500 µm |
| No. 4 | 4.750 mm | 4750 µm |
| No. 8 | 2.360 mm | 2360 µm |
| No. 16 | 1.180 mm | 1180 µm |
| No. 30 | 600 µm | 0.600 mm |
| No. 50 | 300 µm | 0.300 mm |
| No. 100 | 150 µm | 0.150 mm |
| No. 200 | 75 µm | 0.075 mm |
How to specify a sieve so it cannot be misread
- Give the aperture. “150 µm” is unambiguous; “100 mesh” is not.
- Name the standard. ASTM E11, ISO 3310-1 and BS 410 are different aperture series and are not interchangeable by number.
- Give the frame. Diameter and height, in millimetres or inches.
- Give the material. Woven wire grade and frame material — 304 or 316 stainless, or brass.
- Ask for the certificate. A nominal aperture is a target; the tolerance is what your result depends on.
Take it to the bench. The same two tables as a printable A4 sheet — the 21-grade chart with conflict flags, the full ASTM E11 series, C136 aggregate sizes, and the five rules for writing an unambiguous sieve specification.
Related reading. How to choose the correct test sieve — 6–40 cm frames · Build a particle size analysis workstation · All applications
Aperture values are nominal for the mesh grades shown. ASTM E11 values are the nominal apertures of the woven-wire test sieve series, cross-checked against two independent published tables of the standard. ISO 3310-1 and BS 410 are separate aperture series and are not interchangeable with ASTM E11 by number. This page is a reference aid, not a substitute for the standard itself or for the certificate that ships with your sieves.
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