Does mesh count alone define the opening?

No. Clear opening is 1/N minus the wire diameter, where N is the mesh count per inch. Two screens of the same mesh count woven with different wire diameters have different openings and different open areas, so a screen must never be specified by mesh count alone.

Is mesh to micron conversion exact?

No. It depends on wire diameter and on the sieve standard in use, and standard sieve designations carry nominal apertures rather than exact conversions of the inch figure. Cross-standard equivalence is approximate and should be labelled as such in any specification.

Is the opening the same as particle retention?

No. Nominal aperture is a geometric dimension. Actual retention depends on particle shape, concentration, fluid velocity, whether the particles are deformable and how far the element has already loaded. A screen with a 140 micron opening does not guarantee removal of every particle above 140 micron.

Mesh to Micron Converter for Strainer Screens

Purpose

Why This Is Not a Simple Lookup

A mesh count is a weave density — the number of openings per inch. It is not an opening. The clear opening is what is left once the wire is taken out: 1/N − wire diameter. Two screens both called 100 mesh, woven with different wire, have different openings and different open areas. That is why this converter always shows the wire diameter it used, and tells you where that figure came from.

When to use it

Translating a customer's "100 mesh" into an opening you can engineer with.
Checking a supplier's micron claim against the weave they actually quoted.
Writing a screen specification that states opening and wire diameter.

What it will not tell you

Absolute particle retention. Aperture is geometry; retention is behaviour.
Exact equivalence between sieve standards — those are nominal designations.
Whether the screen is strong enough. That is a separate check.

Converter

Convert an Opening

Results update as you type.

Input

Start from a mesh count, or from an opening you already know.

Convert from

Mesh count (per inch)

Wire diameter

Leave blank to use the reference weave.

That wire diameter leaves no opening at this mesh count.

Result

Clear opening

—

Opening, millimetres	—
Opening, inches	—
Mesh count	—
Wire diameter used	—
Open area	—
Typical retention duty	—

Plain square weave, drawn to the computed opening and wire

Methodology

Formulae, Sources and Limits

a = 1 / N − d_w Clear opening of a plain square weave, in inches. N mesh count per inch, d_w wire diameter in inches.

OA% = (1 − N × d_w)² × 100 Open area. Source: standard woven wire formula, as published by the woven wire industry (wovenwire.com, Square Mesh Open Area Formula). Algebraically the same as (a / (a + d_w))² × 100, since a + d_w = 1/N.

µm = a × 25 400 Inch to micron. Note this is the computed aperture; a standard sieve designation may carry a slightly different nominal value.

Reference weaves are taken from the Hydrotherms Engineering Handbook, chapter 7.2. Every row was re-derived from 1/N − d_w before being used here.

The three limits that matter

Mesh count is not an opening. It is openings per inch. The opening depends on the wire, and the wire is a free variable the weaver chooses.
Standards are not interchangeable. A sieve designation carries a nominal aperture fixed by its standard, which is not always the exact conversion of the inch figure. Cross-standard equivalence is approximate — label it as such.
Aperture is not retention. Retention depends on particle shape, concentration, velocity, deformability and how loaded the element already is. A 140 µm opening does not guarantee removal of everything above 140 µm.

Assumptions

Plain square weave. Twill, Dutch and reverse Dutch weaves do not follow this formula.
Nominal wire diameter, no manufacturing tolerance applied.
No support plate is considered.

Reference

Woven Wire Reference Table

Type a mesh count, a wire diameter or a micron figure to filter.

Mesh	Wire dia (in)	Clear opening (in)	Opening (µm)	Open area %
2	0.0630	0.4370	11100	76.4
2	0.0920	0.4070	10360	66.6
3	0.0630	0.2700	6860	65.6
4	0.0470	0.2080	5160	65.9
4	0.0630	0.1870	4750	56.0
5	0.0410	0.1590	4040	63.2
6	0.0350	0.1320	3350	62.7
7	0.0350	0.1080	2740	57.2
8	0.0280	0.0970	2460	60.2
10	0.0250	0.0750	1905	56.3
11	0.0180	0.0730	1850	64.5
12	0.0230	0.0600	1520	51.8
14	0.0200	0.0510	1300	51.0
16	0.0180	0.0440	1130	50.7
18	0.0170	0.0380	980	48.3
20	0.0160	0.0340	872	46.2
30	0.0130	0.0200	513	37.1
40	0.0100	0.0150	384	36.0
50	0.0090	0.0110	282	30.3
60	0.0070	0.0090	231	33.9
80	0.0050	0.0075	180	36.0
100	0.0045	0.0055	141	30.0
120	0.0037	0.0046	118	30.1
150	0.0026	0.0041	105	37.4
170	0.0024	0.0035	79	35.1
200	0.0021	0.0029	74	33.6
250	0.0016	0.0024	62	36.0
300	0.0015	0.0018	46	29.7
325	0.0014	0.0017	44	30.0
400	0.0010	0.0015	39	36.0

The micron column carries the nominal standard aperture. Where it differs slightly from the inch figure converted, that is not an error — it is the standard's designated value, and it is exactly why equivalence between standards must be treated as approximate.

Technical FAQ

Questions Engineers Ask

Someone specified "100 mesh". Is that enough?

No. Ask for the wire diameter, or for the opening in micron. At 100 mesh the opening can vary by a third depending on the wire, and the open area with it.

Why do two tables disagree?

Because they are built on different standard wires, or different sieve standards. Neither is wrong; they are answering slightly different questions.

Does finer always mean better protection?

No. A finer screen blocks faster, raises pressure drop and shortens the cleaning interval. Choose the coarsest opening that protects the equipment downstream.

What should a specification say?

Material, weave, mesh count, wire diameter, nominal opening, open area, support construction and the differential pressure the element must withstand.

Next Step

Get This Selection Verified by Hydrotherms

An opening is the start of a screen specification, not the end of one. Send us the duty and we will come back with the weave, the support construction and the differential pressure the element can actually take.

Get This Verified Open Area Calculator

Calculation version MMC-1.0 Last technical review 28 August 2026 Reviewed by Hydrotherms engineering

Engineering disclaimer. Preliminary engineering guidance. Does not replace the applicable design code, project specification, piping class, statutory requirement or certified manufacturer data.