Fineness is the single most important number in a pulverizer specification — and the most often misunderstood. This guide converts mesh to micron and explains how to state particle size so that a powder grinding machine can be sized correctly.
What does “mesh” mean?
Mesh is the number of openings per linear inch of a sieve. Higher mesh means smaller openings. Because wire thickness varies, the opening size is defined by standards such as ASTM E11 (US) and IS 460 (India). The micron (µm) value is the meaningful physical measure.
Mesh to micron chart
| US mesh (ASTM E11) | Opening (µm) | Opening (mm) | Typical product |
|---|---|---|---|
| 20 | 850 | 0.850 | Coarse grits |
| 30 | 600 | 0.600 | Coarse ground spices |
| 40 | 425 | 0.425 | Feed meal, coarse powders |
| 50 | 300 | 0.300 | Masala blends |
| 60 | 250 | 0.250 | Standard spice powder (lower end of impact pulverizer range) |
| 80 | 180 | 0.180 | Chilli and turmeric powder |
| 100 | 150 | 0.150 | Fine spices, powdered sugar (~150 mesh = 100 µm per Premium Pulman) |
| 120 | 125 | 0.125 | Fine flours |
| 140 | 106 | 0.106 | Fine chemicals |
| 170 | 90 | 0.090 | Pharma and food powders |
| 200 | 75 | 0.075 | Fine powders (turbo classifier lower range) |
| 230 | 63 | 0.063 | Very fine |
| 270 | 53 | 0.053 | Very fine |
| 325 | 45 | 0.045 | Upper end of impact pulverizer range |
| 400 | 38 | 0.038 | Ultrafine (turbo classifier upper range) |
| 500 | 25 | 0.025 | Ultrafine |
| 635 | 20 | 0.020 | Finest standard sieve |
Sieves finer than 635 mesh are not standard; below ~20 µm, specify particle size in microns measured by laser diffraction.
How to specify fineness
- Sieve pass: “minimum 98% passing 80 mesh (180 µm)”.
- Percentile: d50 = median size; d97 = 97% of particles are smaller. Ultrafine products are usually specified by d97.
- Top size matters: a few coarse particles can fail a sieve test even if the average is fine.
- Test method: dry sieving, wet sieving (for agglomerating powders) or laser diffraction — agree it with the supplier.
Which machine reaches which size?
| Machine | Manufacturer-stated fineness |
|---|---|
| Miracle Mill | Up to 150 mesh (100 µm) on sugar |
| Micro Pulverizer | Up to 250 mesh; ~20 µm on sugar |
| Pin Mill | Up to 300 mesh (50 µm) on sugar |
| Impact Pulverizer | 60–325 mesh |
| Turbo Classifier Mill | 200–450 mesh (75–37 µm); ~10 µm on sugar |
Remember that achievable fineness depends on the material: fibrous, oily or hard materials will not reach the same size as sugar on the same machine.
Frequently Asked Questions
How many microns is 100 mesh?
A 100 mesh ASTM sieve has 150 µm openings.
How many microns is 200 mesh?
75 µm.
How many microns is 325 mesh?
45 µm.