Particle D50 & Mesh Conversion Guide

1. Basic Definitions

1. Mesh

Mesh is a standard unit for sieving. It is defined as the number of sieve openings within one inch (25.4 mm) length.

• Higher mesh number → smaller sieve opening → finer particles;
• Lower mesh number → larger sieve opening → coarser particles.

2. D50 Median Particle Size

Measured by laser particle size analyzer. 50% of all particles are smaller than this value and 50% are larger. It stands for the overall average particle size, unit: micrometer (μm).

2. Relationship between D50 and Mesh

1. They are not absolutely equivalent mathematically. Mesh depends on sieve aperture, while D50 depends on overall particle size distribution. For powder passing the same sieve, D50 may vary due to particle shape and distribution range.

2. General rule: Higher mesh → smaller sieve aperture → lower D50 value. They are negatively correlated.

3. Applicable range: Conversion error is very small for coarse powder (≤ 400 mesh). For ultra-fine powder (≥ 800 mesh), results are for reference only due to particle agglomeration and wide distribution.

3. Standard Conversion Formulas (Industry Standard)

Industry simplified formulas (ignoring sieve wire diameter, widely used in engineering):

Additional Notes:

• This is an approximate engineering formula, widely used for product selection, quotation and technical communication in powder industry.
• Standard national sieves include wire diameter, so actual aperture is slightly smaller. No correction is required for industrial application.
• Round off the result to integer; mesh number does not use decimals.

Calculation Examples:

Example 1: Powder D50 = 20 μm, calculate corresponding mesh

Mesh = 25400 ÷ 20 = 1270 mesh

Example 2: Powder D50 = 50 μm, calculate corresponding mesh

Mesh = 25400 ÷ 50 = 508 mesh

4. Important Remarks

• 1. D50 is average particle size, not maximum particle size. Do not use D90 for mesh conversion.
• 2. For flaky, needle-shaped or fibrous irregular particles, sieving performance differs from spherical particles. Conversion result is for reference only.
• 3. Nano powder (D50 ＜ 1 μm) is no longer marked by mesh; particle size is described in μm or nm uniformly.
• 4. Slight differences exist between international standards (Tyler sieve, GB sieve). This table adopts general industrial standards.