Mesh to Micron Conversion

Mesh and micron both describe particle size, but they do it in different ways.

Mesh usually refers to the number of openings in a screen per linear inch.

Micron means micrometer, equal to one millionth of a meter.

1 micron = 1 µm = 0.001 mm
1 mm = 1,000 µm

The important point:

Mesh does not convert to microns with one universal formula.

The micron opening depends on the sieve standard, the wire diameter, and the nominal aperture size. For laboratory and industrial work, use a standard sieve table rather than guessing from mesh count alone.

Quick Mesh to Micron Chart

These are common U.S. Standard sieve sizes and their nominal openings.

U.S. Mesh	Opening
4 mesh	4,750 µm
6 mesh	3,350 µm
8 mesh	2,360 µm
10 mesh	2,000 µm
12 mesh	1,700 µm
14 mesh	1,400 µm
16 mesh	1,180 µm
18 mesh	1,000 µm
20 mesh	850 µm
25 mesh	710 µm
30 mesh	600 µm
35 mesh	500 µm
40 mesh	425 µm
45 mesh	355 µm
50 mesh	300 µm
60 mesh	250 µm
70 mesh	212 µm
80 mesh	180 µm
100 mesh	150 µm
120 mesh	125 µm
140 mesh	106 µm
170 mesh	90 µm
200 mesh	75 µm
230 mesh	63 µm
270 mesh	53 µm
325 mesh	45 µm
400 mesh	38 µm

This chart is a practical reference, not a replacement for a purchasing specification. For critical work, specify the standard and the actual aperture size.

What Does Mesh Mean?

Mesh describes how many openings a screen has per linear inch.

For example:

10 mesh = about 10 openings per inch
100 mesh = about 100 openings per inch

As mesh number increases, the openings generally get smaller.

That means:

low mesh number = larger openings
high mesh number = smaller openings

So a 20 mesh screen has larger openings than a 200 mesh screen.

The confusing part is that the mesh number alone does not tell you the exact open space. Wire thickness matters too.

What Does Micron Mean?

A micron is a micrometer.

It is a direct unit of length:

1 µm = 0.001 mm
1,000 µm = 1 mm

Microns describe the actual opening size or particle size.

For example:

75 µm = 0.075 mm
850 µm = 0.850 mm

When a material is described as passing a 75 µm sieve, that is usually more precise than saying it passes a 200 mesh sieve, because the aperture is stated directly.

Why Mesh Does Not Have One Exact Formula

It is tempting to use a simple formula such as:

Microns ≈ 14,900 ÷ mesh

This rough shortcut can be close for some common fine mesh sizes.

For example:

14,900 ÷ 200 = 74.5 µm

That is close to the common 200 mesh = 75 µm value.

But the shortcut fails badly for other sizes.

For 20 mesh:

14,900 ÷ 20 = 745 µm

The common standard opening is:

20 mesh = 850 µm

The difference is large enough to matter in screening, filtration, powder processing, and quality control.

Use the formula only for rough mental estimation. Use a standard table for specifications.

Why Wire Diameter Matters

Mesh count tells you how many openings fit in an inch.

But each opening is separated by wire.

If the wire is thicker, the open space is smaller.

If the wire is thinner, the open space is larger.

That is why two screens with the same mesh count can have different opening sizes if they use different wire diameters or different sieve standards.

For test sieves, standards define nominal aperture sizes, tolerances, and construction requirements so that sieve results are comparable.

ASTM E11 and ISO Sieve Standards

For U.S. test sieves, a common reference is ASTM E11.

ASTM describes E11 as the standard specification for woven wire test sieve cloth and test sieves. The standard covers requirements for sieve cloth, test sieve construction, and inspection procedures for classifying material by particle size.

External reference: ASTM E11 Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves

For international sieve work, two important ISO references are:

ISO 3310-1:2016, which specifies technical requirements and test methods for metal wire cloth test sieves.
ISO 565:1990, which defines nominal opening sizes for test sieves.

ISO 3310-1 applies to test sieves with aperture sizes from 125 mm down to 20 µm, in accordance with ISO 565.

The practical lesson is simple:

For serious work, identify the sieve standard, not just the mesh number.

How to Convert Mesh to Micron

For real specifications, convert mesh to micron by looking up the standard aperture size.

Use this process:

Identify the mesh system or sieve standard.
Look up the nominal opening size.
Record the aperture in microns or millimeters.
Include the standard in your specification.

Example: Convert 100 Mesh to Microns

From the common U.S. Standard sieve table:

100 mesh = 150 µm

So a 100 mesh sieve has a nominal opening of:

150 microns

Example: Convert 200 Mesh to Microns

From the common U.S. Standard sieve table:

200 mesh = 75 µm

So a 200 mesh sieve has a nominal opening of:

75 microns

Example: Convert 325 Mesh to Microns

From the common U.S. Standard sieve table:

325 mesh = 45 µm

So a 325 mesh sieve has a nominal opening of:

45 microns

How to Convert Micron to Mesh

To convert microns to mesh, find the closest sieve opening in the table.

Example: Convert 250 Microns to Mesh

Look up 250 µm.

The common table gives:

60 mesh = 250 µm

So:

250 microns is approximately 60 mesh

Example: Convert 75 Microns to Mesh

Look up 75 µm.

The common table gives:

200 mesh = 75 µm

So:

75 microns is approximately 200 mesh

Example: Convert 100 Microns to Mesh

The common table does not list exactly 100 µm.

Nearby values are:

120 mesh = 125 µm
140 mesh = 106 µm
170 mesh = 90 µm

So 100 µm is between 140 mesh and 170 mesh.

For a specification, write the actual aperture:

100 µm sieve opening

rather than forcing it into an approximate mesh number.

Mesh Size and Particle Size

Sieve language often uses phrases like:

-200 mesh
+200 mesh

These signs matter.

-200 mesh usually means the material passes through a 200 mesh sieve.

Since 200 mesh is commonly 75 µm, -200 mesh means particles are generally smaller than the sieve opening.

+200 mesh usually means the material is retained on a 200 mesh sieve.

That means particles are generally larger than the sieve opening.

Always check the context, because industries may use shorthand differently.

Mesh vs Micron vs Millimeter

Microns and millimeters are direct length units.

Mesh is a screen count.

Unit	Meaning
Mesh	Openings per linear inch, tied to a sieve table
Micron	One millionth of a meter
Millimeter	One thousandth of a meter

To convert between microns and millimeters:

Microns = Millimeters × 1,000

Millimeters = Microns ÷ 1,000

Examples:

850 µm = 0.850 mm
75 µm = 0.075 mm
38 µm = 0.038 mm

Common Mesh to Micron Examples

20 Mesh to Micron

Common U.S. Standard opening:

20 mesh = 850 µm

This is also:

0.850 mm

40 Mesh to Micron

Common U.S. Standard opening:

40 mesh = 425 µm

This is:

0.425 mm

60 Mesh to Micron

Common U.S. Standard opening:

60 mesh = 250 µm

This is:

0.250 mm

100 Mesh to Micron

Common U.S. Standard opening:

100 mesh = 150 µm

This is:

0.150 mm

200 Mesh to Micron

Common U.S. Standard opening:

200 mesh = 75 µm

This is:

0.075 mm

400 Mesh to Micron

Common U.S. Standard opening:

400 mesh = 38 µm

This is:

0.038 mm

What Mesh Size Means in Practice

Mesh-to-micron conversion appears in many industries.

Powder Processing

Powders are often classified by what sieve they pass through.

For example:

Material passing 100 mesh

often means particles pass through a nominal 150 µm opening.

Filtration

Filter screens may be described by mesh or micron rating.

For filtration, micron rating is often easier to interpret because it directly describes particle size.

Aggregates and Soil

Sieve analysis is used to describe particle size distribution.

The result may report how much material is retained on or passes through each sieve.

Food, Pharma, and Chemicals

Powder size can affect flow, blending, dissolution, texture, and quality control.

In regulated or quality-sensitive work, use the actual sieve standard and aperture size.

Choosing a Mesh Size

Choose mesh size based on the particle size you want to pass or retain.

Ask:

What is the maximum particle size allowed?
Should the material pass through the screen or be retained on it?
Is the specification based on U.S. Standard, Tyler, ASTM, ISO, or another system?
Does the application require certified test sieves?
Are tolerances important?

For casual work, a conversion chart may be enough.

For lab, production, or purchasing work, specify:

Sieve standard
Nominal aperture
Mesh designation if needed
Tolerance or certification level if required

Common Mistakes

Treating Mesh as a Direct Unit of Length

Mesh is not a length unit.

Micron is a length unit.

That is why mesh-to-micron conversion requires a table.

Using the 14,900 Shortcut as a Specification

The shortcut can be useful for quick estimates, but it is not reliable enough for ordering screens or writing quality-control requirements.

Use the standard aperture value instead.

Ignoring the Sieve Standard

U.S. Standard mesh, Tyler mesh, ISO sieve sizes, and manufacturer-specific screens may not match exactly.

If the application matters, name the standard.

Confusing Passing and Retained Material

-200 mesh and +200 mesh mean different things.

One refers to material passing the sieve.

The other refers to material retained on the sieve.

Rounding Too Aggressively

Small differences matter at fine particle sizes.

For example:

45 µm and 38 µm

are close in everyday language, but they correspond to different common sieve openings.

Frequently Asked Questions

What is mesh to micron conversion?

Mesh to micron conversion maps a sieve mesh number to its nominal opening size in micrometers.

For example:

200 mesh = 75 µm

in the common U.S. Standard sieve table.

Is there a formula to convert mesh to microns?

There is no universal exact formula.

A rough shortcut is:

Microns ≈ 14,900 ÷ mesh

But this is only an estimate. For specifications, use a standard sieve table.

What is 100 mesh in microns?

Common U.S. Standard opening:

100 mesh = 150 µm

What is 200 mesh in microns?

Common U.S. Standard opening:

200 mesh = 75 µm

What is 325 mesh in microns?

Common U.S. Standard opening:

325 mesh = 45 µm

What mesh is 250 microns?

Common U.S. Standard opening:

250 µm = 60 mesh

What mesh is 75 microns?

Common U.S. Standard opening:

75 µm = 200 mesh

Is higher mesh finer?

Yes, generally.

A higher mesh number usually means smaller openings and finer particles.

For example:

20 mesh = 850 µm
200 mesh = 75 µm

So 200 mesh is much finer than 20 mesh.

Should I specify mesh or microns?

For informal communication, mesh may be enough.

For technical specifications, microns are clearer because they state the opening size directly.

For critical work, specify both the standard and the nominal aperture.

Sources and Standards

For deeper reference, use the standards behind the sieve sizes:

These standards are the right place to start when sieve tolerances, certification, or formal compliance matters.

Sieve reports often include percent passing or percent retained. If you need a refresher on those percentage calculations, see How to Calculate Percentage.

Final Thoughts

Mesh to micron conversion is simple only when you use the right table.

The safest habit is:

Use mesh as a sieve designation.
Use microns as the actual opening size.

For quick reference, 100 mesh is commonly 150 µm, 200 mesh is commonly 75 µm, and 325 mesh is commonly 45 µm.

For real specifications, do not rely on a rough formula. State the sieve standard, the nominal aperture size, and the mesh designation if it helps the reader connect the two.