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Mesh to Micron.

Convert between US/Tyler sieve mesh numbers and micron openings using ASTM E11, with particle-size classification and a sub-sieve milling reference.

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Load example mesh to micron converter data to see the full workflow

Value

Input unit

Standard

Opening

45.0 µm

Opening (mm)

0.045 mm

Nearest sieve

325 mesh

Classification

Fine

When to use

Converting a sieve-specification mesh number to microns for an analytical method or SOP
Looking up the nearest standard sieve to pass or retain a target particle size
Cross-referencing ASTM E11 and Tyler values when comparing legacy protocols
Determining whether a target particle size falls within the sieve range or requires milling
Exporting a conversion record for a lab notebook or regulatory submission

Do not use for

For particle sizes below ~20 µm — use a ball mill and laser diffraction instead of sieving
As a substitute for actual sieve analysis — the converter reports nominal openings, not measured particle-size distributions
When working with non-spherical particles where the relevant dimension is not equivalent spherical diameter
For ISO/BS 410 (UK) or DIN 4188 (German) sieve standards — this converter covers ASTM E11 and Tyler only

ASTM 325 mesh = 45 µm, not 44 µm

The ASTM E11 standard specifies 45 µm for a 325-mesh sieve. The Tyler series gives 43 µm. Many older references cite 44 µm (a rounded average). When your protocol specifies 325 mesh, confirm which standard it follows — the 2 µm difference can matter for fine-powder specifications.

Mesh number and opening are inversely related

Higher mesh number = finer opening = smaller particles passing through. A 325-mesh sieve is much finer than a 100-mesh sieve (150 µm). This is counterintuitive to users new to sieve notation. The mesh number counts wires per linear inch, so more wires = smaller gaps.

Sieve fractionation ≠ particle-size distribution

A sieve pass/retain result tells you the fraction of particles above or below a single cut size. It does not give you a distribution (D10/D50/D90). For specification work requiring a full distribution, combine sieve analysis with laser diffraction or sedimentation.

Sub-sieve targets require milling, not finer sieves

If your target is below ~44 µm (325 mesh), wire-cloth sieves cannot make the cut. Planetary ball milling is the standard laboratory route to the sub-sieve range, reaching 0.1 µm with the right media and cycle. The size-spectrum ruler in this tool shows exactly where sieving stops and milling takes over.

Method

Mesh → micron uses an exact lookup against the ASTM E11 or Tyler table; off-table mesh numbers use log-linear interpolation between the two nearest bracketing points: $\mu m = \exp(\ln(\mu m_{lo}) + t \cdot (\ln(\mu m_{hi}) - \ln(\mu m_{lo})))$ where $t = (\ln(mesh) - \ln(mesh_{lo})) / (\ln(mesh_{hi}) - \ln(mesh_{lo}))$ . Micron → mesh applies the inverse on the same table. The nearest standard sieve is found by minimizing $|\mu m_{table} - \mu m_{input}|$ . Classification bands: Coarse > 2000 µm; Medium 250–2000 µm; Fine 44–250 µm; Very fine 10–44 µm; Ultrafine / sub-sieve < 10 µm.

Published

Published 2026-06-14. Calculations support planning and documentation; verify procurement decisions against manufacturer specifications or institutional SOPs.

How to cite

How to Cite

ConductScience Mesh to Micron Converter. ConductScience, Inc. 2026. Available at: https://conductscience.com/tools/mesh-to-micron-converter

ASTM International. ASTM E11: Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves. ASTM International; 2022.

Allen T. Particle Size Measurement, 5th ed. Chapman & Hall; 1997.

International Organization for Standardization. ISO 565: Test Sieves — Metal Wire Cloth, Perforated Metal Plate and Electroformed Sheet. ISO; 2020.

ASTM E11 and Tyler Mesh Standards

Two sieve series are in common use in North American and international laboratories.

ASTM E11 (US Standard Sieve)

Maintained by ASTM International and harmonized with ISO 565/3310-1. Openings are specified in millimeters (or micrometers for fine sieves) rather than mesh count, but mesh numbers are widely used informally. Regulatory filings in the US (USP, ASTM methods, EPA methods) reference ASTM E11. Key reference points: 200 mesh = 75 µm, 325 mesh = 45 µm, 400 mesh = 38 µm, 500 mesh = 25 µm, 635 mesh = 20 µm.

Tyler Mesh Series

An older industrial standard historically used in mining, geology, and comminution. Tyler mesh numbers are close but not identical to ASTM for many sizes. Key Tyler points: 200 mesh = 74 µm, 270 mesh = 53 µm, 325 mesh = 43 µm, 400 mesh = 38 µm. When reading legacy protocols or published particle-size data, confirm which standard was used.

When standards agree and disagree

For coarse sieves (< 100 mesh) the two series diverge substantially in mesh number for the same opening. For finer sieves the nominal openings are close but differences of 2–5 µm are significant when targeting 44 µm (325 mesh) specification tolerances.

Log-space interpolation

Between tabulated standard points, opening and mesh number follow an approximately geometric (log-linear) relationship. This converter uses log-space interpolation to estimate openings for non-standard mesh numbers, which gives more accurate results than linear interpolation across a series that spans nearly 5 orders of magnitude (0.1 µm to 25 mm).

Particle Size in Lab Sample Preparation

Particle size affects virtually every downstream measurement: extraction efficiency, dissolution rate, spectroscopic signal, chromatographic resolution, and immunoassay homogeneity. Understanding where your target size falls in the broader spectrum helps you choose the right method.

Geological size classes (Wentworth/ISO 14688)

Gravel: > 2 mm — crushed, not sieved in most lab work
Sand: 63 µm – 2 mm — sieve-fractionable, ASTM sieves 10–230
Silt: 2 – 63 µm — fine sieves, transitioning to air classification
Clay: < 2 µm — sub-sieve; requires sedimentation or laser diffraction

Sieve range vs. milling range

Standard wire-cloth sieves are practical down to approximately 20–38 µm (ASTM 635–400 mesh). Below that, particles bridge the mesh, electrostatic forces dominate gravity, and separations become unreliable. Planetary ball milling extends the practical range from the coarse sieve floor down to approximately 0.1 µm for hard brittle materials — roughly 3.5 decades below where sieving stops.

Measurement methods by size range

> 45 µm: dry or wet sieving (ASTM E11 / Tyler)
1–2000 µm: laser diffraction (ISO 13320); reports D10/D50/D90
0.01–10 µm: dynamic light scattering (DLS / photon correlation spectroscopy)
< 1 µm (nanoparticles): DLS, TEM, BET surface area

Report the measurement method alongside the size value — D50 by laser diffraction and sieve-pass size are not interchangeable.

Sub-sieve milling note

When your target size falls in the Very fine (10–44 µm) or Ultrafine/sub-sieve (< 10 µm) band, sieving cannot be used to confirm the result. Planetary ball milling to the target size followed by laser diffraction is the standard analytical sample-prep workflow. The BKBM-V2S reaches 0.1 µm minimum output with appropriate media and cycle time.

Frequently asked

What is 325 mesh in microns?

Per ASTM E11, a 325 mesh sieve has a nominal opening of 45 µm. Per the Tyler series, 325 mesh corresponds to 43 µm. The slight difference arises from independent wire-diameter specifications in each standard. Use this converter to look up any mesh number in either standard and see the exact tabulated opening.

ASTM E11 vs Tyler — which standard should I use?

ASTM E11 (US standard sieve) is the current ISO-aligned standard used in most US laboratories and referenced by USP, ASTM methods, and regulatory submissions. Tyler mesh is an older industrial series still common in mining, geology, and some legacy process-industry specifications. If your SOPs do not specify a standard, use ASTM E11. If you are comparing results from an older literature source, check whether it used Tyler — the mesh numbers are similar but not identical for finer sieves (e.g. Tyler 270 = 53 µm, ASTM 270 = 53 µm, but Tyler 325 = 43 µm vs ASTM 325 = 45 µm).

Why can't sieving reach sub-micron particle sizes?

Woven-wire sieves have practical lower limits around 20–38 µm (ASTM 635 and 400 mesh). Below that range, particles clog the mesh, electrostatic forces dominate gravity, and reproducible separation becomes unreliable. For sub-sieve work — powders below ~44 µm (325 mesh) and especially below 10 µm — mechanical milling (planetary ball mill, bead mill) followed by laser diffraction or sedimentation-based particle-size analysis is the standard approach.

How fine can a planetary ball mill grind?

A high-energy planetary ball mill such as the Vertical Planetary Ball Mill (BKBM-V2S) can reduce hard brittle materials to approximately 0.1 µm (100 nm) under optimal conditions — roughly 450× finer than what a 325-mesh sieve can pass. This is the practical floor for most laboratory planetary mills using zirconia or tungsten carbide media. The size-spectrum ruler in this converter marks that 0.1 µm threshold so you can visualize how far below the sieve range milling can reach.

How is micron-to-mesh interpolation calculated?

For an exact table entry the converter returns the tabulated value directly. For off-table values it uses log-linear interpolation between the two nearest bracketing sieve points: mesh = exp( ln(mesh_lo) + (ln(µm) − ln(µm_hi)) / (ln(µm_lo) − ln(µm_hi)) × (ln(mesh_hi) − ln(mesh_lo)) ). Log-space interpolation is appropriate because sieve openings and mesh numbers follow approximately geometric progressions. The converter also reports the nearest actual standard sieve for practical use.

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