Mesh to micron conversion answers one question: how fine is the powder I am buying or producing? Mesh counts the openings per inch in a sieve screen. Microns measure the actual particle size. Buyers in different regions use different units, and a quote that says “200 mesh” and a certificate that says “75 µm” describe the same powder.
This guide gives you the full conversion chart, a quick mental formula, the difference between D-values and mesh, and typical mesh specifications by industry.
The quick rule: Mesh × Microns ≈ 15000
When you have no chart nearby, multiply the mesh number by its aperture in microns. The product stays close to 15,000 across the mid-range:
- 100 mesh × 150 µm = 15,000
- 200 mesh × 75 µm = 15,000
- 325 mesh × 45 µm ≈ 14,600
- 400 mesh × 38 µm ≈ 15,200
Divide 15,000 by the mesh number to get microns, or divide 15,000 by the micron size to get mesh. The rule drifts at the coarse and fine ends, so use the full table below when the number matters to a specification.
Worked examples, both directions
From mesh to microns: a supplier offers 270 mesh calcium carbonate. 15,000 ÷ 270 ≈ 56 µm. The largest particles will pass through a 53 to 63 µm aperture.
From microns to mesh: your process needs powder below 20 µm. 15,000 ÷ 20 = 750. Standard sieves stop at 635 mesh, which is why powders this fine are always specified in microns and measured by laser diffraction, not sieves.
Full mesh to micron conversion chart (ASTM E11)
The table lists US standard sieve sizes. 1 mm = 1,000 µm.
| Mesh | µm | Mesh | µm | Mesh | µm |
|---|---|---|---|---|---|
| 4 | 4,750 | 45 | 355 | 170 | 90 |
| 6 | 3,350 | 50 | 300 | 200 | 75 |
| 8 | 2,360 | 60 | 250 | 230 | 63 |
| 10 | 2,000 | 70 | 212 | 270 | 53 |
| 12 | 1,700 | 80 | 180 | 325 | 45 |
| 14 | 1,400 | 100 | 150 | 400 | 38 |
| 16 | 1,180 | 120 | 125 | 500 | 25 |
| 20 | 850 | 140 | 106 | 635 | 20 |
| 24 | 710 | ||||
| 30 | 600 | ||||
| 35 | 500 | ||||
| 40 | 425 |
325 mesh equals 45 µm, and it is the most quoted specification in mineral powder trade. Above roughly 400 mesh, sieving becomes slow and unreliable, which is why finer powders switch to micron or D-value specifications.
Why charts sometimes disagree
Two charts can give slightly different micron values for the same mesh, and both can be correct. Mesh describes the number of openings per inch, but the aperture depends on the wire diameter. Standards bodies set different wire sizes:
- ASTM E11 (US): 200 mesh = 75 µm
- Tyler (US, industrial): 200 mesh = 74 µm, with a different mesh series at some sizes
- ISO 3310 (international): apertures in rounded microns, 75 µm instead of a mesh number
Differences stay within a few percent. They matter only when a customer caps a value at, for example, “not more than 45 µm”, so confirm which standard the certificate uses.
Mesh, D10, D50, D90 and D97: not the same thing
A sieve tells you whether a particle passes a hole. Laser diffraction tells you the full size distribution. Both appear in specifications, and mixing them up causes disputes.
If D10 = 3 µm, D50 = 10 µm and D90 = 12 µm, then 10% of particles are smaller than 3 µm, half are smaller than 10 µm, and 90% are smaller than 12 µm. D50 is the median. D90 caps the coarse side of the main distribution.
D97 works the same way: 97% of particles fall below it. Buyers use D97 to control the tail of oversize particles, because a small number of coarse particles ruins coatings, inks and suspensions even when the D90 looks fine. A powder can pass a 325 mesh sieve and still fail a D97 of 20 µm, because the sieve only proves no particle is above 45 µm, not where the rest sit.
Use mesh for coarse powders and incoming inspection. Use D-values for anything finer than about 400 mesh.
Typical mesh specifications by industry
| Application | Typical spec | Approx. µm |
|---|---|---|
| Glass sand, foundry | 20 to 70 mesh | 850 to 212 |
| Construction filler, artificial stone | 40 to 120 mesh | 425 to 125 |
| Paper and paint filler (GCC) | 325 to 635 mesh, often as D97 | 45 to 20 |
| Food and pharmaceutical excipients | 100 to 300 mesh, as D90 or D97 | 150 to 50 |
| Ultrafine fillers, battery materials | D97 below 30 µm | below 30 |
Specifications tighten as product value rises. A filler sold by mesh becomes a performance powder sold by D97, and at that point the grinding system matters as much as the raw material. How a jet mill reaches these fineness levels is covered separately.
Which equipment produces which fineness
Match the mill to the target before you look at prices:
- Hammer and pin mills: 20 to 200 mesh, general purpose grinding
- Ball mills with classifiers: 100 to 500 mesh, high volume mineral grinding
- Ring roller mills: 325 to 2,500 mesh, energy efficient fine grinding of non-metallic minerals
- Jet mills: D97 from 45 µm down to 2 µm, no metal contact, the standard for battery and high-purity powders
A jet mill line with integral classifier during assembly. The classifier wheel sets where the top cut lands.
A mill that cannot hold the top cut will fail the specification no matter how fine it grinds on average. That is why classifier selection sits next to grinding in every production line design.
FAQ
How many microns is 325 mesh?
325 mesh equals 45 µm in the ASTM E11 standard. Tyler and ISO values differ by one or two microns.
Is the mesh to micron conversion the same for every material?
Yes for the sieve itself, no for the powder. A 200 mesh screen has a 75 µm aperture regardless of material. But needle-shaped or soft particles pass differently, so the measured distribution can differ from the sieve number.
Why do some charts show different values for the same mesh?
They follow different standards. ASTM, Tyler and ISO set different wire diameters, so apertures shift by a few percent. Always name the standard in your specification.
What is finer than 635 mesh?
Below 20 µm, powders are specified in microns or D-values. Sieves at this level are impractical, and laser diffraction becomes the standard measurement.Send a sample, get the real numbersConverting units is the first step. Holding the target distribution at production volume is the second.
Epic Powder
Epic Powder designs grinding and classifying systems for minerals, chemicals, food, and pharmaceuticals. With more than 20 years of powder processing experience, we match the right mill to your target particle size and capacity. Tell us about your material and we will recommend a tested solution.
Send us your material for a trial grind and we return the D50, D90 and D97 distribution, the throughput, and the specific energy for your target mesh or micron spec, with the mill and classifier combination that holds it.
“Thanks for reading. I hope my article helps. Please leave a comment down below. You may also contact EPIC Powder online customer representative Molly for any further inquiries.”
— Jason Wang, Engineer