If you are searching for how to translate particle size, how to translate mesh to microns, or how to preserve sieve numbers, D10, D50, D90 and particle-size distributions across languages, the first rule is that mesh number and particle diameter are not the same kind of measurement. A “100 mesh” screen describes a sieve convention, while 100 µm describes a physical length. Translating one as though it were a direct synonym for the other can misstate a powder, grain, pigment, pharmaceutical, mineral or filter specification.
Particle-size translation matters in powders, food ingredients, pharmaceuticals, chemicals, minerals, pigments, ceramics, filtration, construction materials, aerosols and laboratory reports. A target-language document can become technically wrong if mesh systems are mixed, if µm is confused with mm, if “passing” and “retained” are reversed, if D50 is treated as a maximum particle size, or if a laser-diffraction distribution is presented as though it came from sieve analysis.
This guide explains how to translate particle-size specifications without changing material meaning. It covers micrometres, millimetres, nanometres, mesh and sieve numbers, aperture size, retained and passing fractions, D10, D50 and D90, median particle size, cumulative distributions, number- versus volume-based distributions, coarse and fine fractions, agglomerates, test methods and how to verify cross-system conversions before publication.
Why particle-size translation needs the measurement method
Particle size sounds simple because it uses familiar units of length, but real materials contain distributions rather than one perfect diameter. A powder may have particles from a few micrometres to hundreds of micrometres, and a report may summarize that distribution with percentile values or sieve fractions.
Mesh is especially easy to mishandle. Mesh number generally relates to the number of openings per linear inch in a particular sieve convention, but wire diameter and standard system affect the actual aperture. A higher mesh number usually indicates a finer opening, which is the opposite numerical direction from micrometre aperture size.
D-values add a different kind of meaning. D50 usually indicates the particle size below which 50% of the measured distribution lies, but the weighting basis—volume, mass or number—depends on the method. Translators should preserve both the percentile label and the analytical context.
A reliable translation method
1. Identify the measurement system
Determine whether the source reports physical diameter, sieve aperture, mesh number, percentile size, aerodynamic diameter, hydrodynamic diameter or another definition. Do not translate every value as generic particle size.
2. Protect the length unit
Keep nm, µm, mm and cm exact. One millimetre equals one thousand micrometres, so a missing prefix changes the size by three orders of magnitude.
3. Keep mesh system and sieve standard visible
If the source names a sieve standard or mesh convention, retain it. Do not assume that a mesh number from one standard has the same aperture as a similarly numbered sieve in another system.
4. Preserve passing and retained direction
“Passing 100 mesh” and “retained on 100 mesh” describe opposite fractions. Translate the preposition and process language with as much care as the number.
5. Preserve D10, D50 and D90 as percentiles
D50 is commonly a median-size descriptor within the reported distribution, not the average of the smallest and largest particle. D90 is not automatically the maximum. Keep the percentile meaning explicit.
6. Keep test method and weighting basis
Laser diffraction, sieving, microscopy, sedimentation and dynamic light scattering can report size differently. If the source identifies volume-based, number-based or mass-based distribution, preserve that basis.
7. Treat conversion tables as approximate mappings
Mesh-to-micron charts can be useful for a stated sieve system, but they are not universal language substitutions. Keep the source mesh number and add an aperture equivalent only when the applicable standard is known.
8. Verify against the specification or laboratory method
Check product datasheets, certificates of analysis, sieve standards and instrument reports. The translated document should describe the same particle population and the same acceptance criterion as the source.
Forty recurring particle-size translation problems
1. Particle size in micrometres
A source such as 50 µm gives a physical length. Preserve the micrometre symbol and value. Do not rename the number as “50 mesh,” because mesh and micrometres describe different measurement systems.
2. Particle size in millimetres
A value such as 0.5 mm can be converted to 500 µm if the target document benefits from another length unit, but the arithmetic must be explicit. Never move the decimal simply because the target market prefers microns.
3. Particle size in nanometres
Nanometre-scale particles are one thousand times smaller than micrometre-scale particles. Preserve nm and µm carefully because automated typography or OCR can erase the distinction.
4. Mesh number
A statement such as 100 mesh should retain the mesh designation and applicable standard. It is not sufficient to translate mesh as “100 openings” without explaining the convention if readers need technical precision.
5. Sieve number
A numbered sieve is an identifier within a standard system. Preserve the sieve designation and, when useful, the nominal aperture stated by the governing standard.
6. Aperture size
A sieve aperture such as 150 µm describes the opening dimension. Keep it distinct from particle diameter because elongated or irregular particles can interact with sieves differently from ideal spheres.
7. Passing fraction
“95% passing 100 mesh” means most of the tested sample passes through the stated sieve. Preserve both the percentage and direction of movement.
8. Retained fraction
“5% retained on 100 mesh” describes the material remaining on the sieve. Translating retained as passing would invert the size distribution.
9. Percent finer
Soil, aggregate and powder reports may use percent finer or percent passing. Preserve the cumulative direction so the target graph or table means the same thing.
10. Percent coarser
A coarser-than fraction describes the opposite side of a cut size. Keep greater-than and less-than relationships explicit.
11. D10
D10 commonly indicates the size below which 10% of the reported distribution lies. Preserve the percentile notation and analytical basis rather than calling it the “smallest particle size.”
12. D50
D50 is commonly a median-size descriptor: half of the reported distribution lies below the stated size under that method and weighting basis. Do not translate it as mean particle size unless the source explicitly defines it that way.
13. D90
D90 describes a high percentile of the distribution. It is not automatically the largest particle present. Preserve its statistical meaning.
14. D95 or D99
Higher percentiles may be used for process control or filtration claims. Keep the exact percentile rather than replacing it with a vague “maximum size.”
15. Mean particle size
Mean size depends on how particles and weighting are defined. Preserve whether the source means arithmetic mean, geometric mean, volume mean or another calculated statistic.
16. Median particle size
Median is a percentile concept, not necessarily the same as average. Translate the statistical term precisely and keep the associated D50 notation if present.
17. Mode particle size
The mode is the most frequent or peak region under a defined distribution representation. Do not replace it with mean or median.
18. Laser diffraction
Laser-diffraction instruments infer a particle-size distribution from light-scattering behavior and an optical model. Preserve the method because its results are not directly interchangeable with sieve results in every material.
19. Sieve analysis
Sieve analysis separates material physically by aperture. Translate sieve stack, shaking time, retained mass and cumulative passing terminology consistently.
20. Microscopy
Image-based particle measurements can report Feret diameter, equivalent circular diameter or other geometric descriptors. Keep the measurement definition rather than calling every result diameter.
21. Dynamic light scattering
DLS commonly reports a hydrodynamic size for dispersed particles. Translate the hydrodynamic concept and do not present the value as a direct physical sieve diameter.
22. Aerodynamic diameter
Aerosol science often uses aerodynamic diameter, which combines size, shape and density effects. Preserve the adjective aerodynamic because it is part of the measurement concept.
23. Volume-based distribution
A volume-weighted particle distribution gives large particles much more influence than a number-weighted distribution. Keep the weighting basis visible in translated reports.
24. Number-based distribution
A number distribution counts particles rather than weighting their volume. The same sample can produce different percentile values depending on representation.
25. Mass-based distribution
Sieving frequently produces mass fractions. Translate weight percent or mass percent carefully rather than assuming it is a number count.
26. Coarse fraction
A coarse fraction must be defined by the stated cut size or sieve. Do not treat coarse as a universal particle-size category.
27. Fine fraction
Fine means smaller than a domain-specific boundary. Preserve the specified limit instead of translating the adjective alone.
28. Fines
In aggregate, mining and powder contexts, fines can mean material below a defined sieve size. Translate both the industry term and the numerical definition where available.
29. Oversize
Oversize material is above a specified cut. Keep the threshold and whether oversize is rejected, recycled or simply reported.
30. Undersize
Undersize material falls below the cut size. Do not reverse it with oversize during target-language reordering.
31. Agglomerate size
Powders may form clusters larger than their primary particles. Translate agglomerate or aggregate terminology so readers know whether the measurement describes primary particles or clusters.
32. Primary particle size
Primary-particle size can differ greatly from agglomerate size. Keep the qualifier primary and the measurement method.
33. Filter rating
A filter rating in micrometres is not automatically the particle size of the feed. Preserve whether the source specifies nominal filter rating, absolute rating or captured-particle size.
34. Powder grade by mesh
Commercial powders may use grade names such as −100 mesh or +200 mesh. Preserve the plus/minus convention and define passing or retained direction if the market could interpret it differently.
35. Particle-size range
A range such as 20–45 µm describes a bounded fraction or nominal specification. Keep both endpoints and do not replace it with a single average value.
36. Maximum particle size
A maximum is a specific upper limit. Do not substitute D90, D95 or a sieve percentile unless the source defines that relationship.
37. Minimum particle size
A minimum is a lower bound and may matter in filtration, coating, printing or packing performance. Preserve greater-than relationships carefully.
38. Bimodal distribution
A bimodal distribution has two distinct peaks. Translating it as simply a broad distribution loses useful information about the material.
39. Span or distribution width
Some reports calculate span from percentile values. Preserve the formula or instrument definition because “spread” can otherwise become vague descriptive language.
40. Mesh-to-micron conversion
If the target document needs both mesh and nominal aperture, identify the sieve standard, use the correct table and retain the original mesh designation. A conversion table is a mapping within a defined standard, not a universal translation dictionary.
Common failure modes
Using mesh and microns as direct synonyms: mesh is a sieve designation; micrometres are length. Keep the underlying system explicit.
Reversing higher mesh and larger particle size: in many mesh systems, a higher mesh number corresponds to a smaller opening. Do not rely on ordinary numerical intuition.
Calling D50 an average: D50 is a percentile descriptor and is often the median of the reported distribution, not automatically the arithmetic mean.
Calling D90 a maximum: D90 leaves a defined fraction above the stated size. It is not necessarily the largest particle.
Dropping the measurement method: sieve, microscopy and laser diffraction may produce different representations for the same material.
Reversing retained and passing: these are opposite directions in sieve analysis and can change pass/fail interpretation.
Dropping distribution basis: number-, volume- and mass-based distributions can produce different percentile values.
Converting without the sieve standard: mesh-to-aperture mapping requires the correct standard or table.
Worked practice
Powder certificate: “D10 8 µm, D50 25 µm, D90 60 µm by laser diffraction.” Preserve all three percentiles and the method. Do not call 60 µm the maximum particle size.
Sieve specification: “95% passing 100 mesh.” Keep percentage, passing direction and mesh system. Add nominal aperture only if the correct sieve standard is known.
Aggregate grading: a table lists cumulative percent passing several sieves. Preserve the cumulative structure so the target grading curve can be reconstructed exactly.
Filter product: “10 µm nominal.” Keep nominal as part of the rating. Do not translate it as an absolute 10 µm capture guarantee.
Nanoparticle dispersion: “Hydrodynamic diameter 120 nm by DLS.” Preserve hydrodynamic and the DLS method rather than simplifying the result to “particle diameter 120 nm.”
Metal powder: “15–45 µm fraction.” Keep the range and the fact that it describes a fraction selected between two cut sizes.
Commercial mesh grade: “−325 mesh.” Preserve the sign convention and explain passing direction if the target market could misread the notation.
Image analysis: a report uses equivalent circular diameter. Translate the full descriptor, because irregular particles do not have one unique geometric diameter.
Sieve standards, instruments and AI
Laboratory reports, certificates of analysis, instrument methods and recognized sieve standards are the strongest references for particle-size translation. They reveal whether a result is based on aperture, equivalent diameter, hydrodynamic behavior, light scattering or another definition.
Conversion charts are useful when they are tied to the correct mesh standard, but translators should preserve the original designation for traceability. If a chart gives only approximate nominal apertures, present them as nominal equivalents rather than exact particle diameters.
AI can explain D-values and convert units, but it may treat D50 as average size or select an arbitrary mesh table. Require the method, weighting basis and sieve standard to be explicit, then verify the result independently.
How this fits the wider eduKate translation system
Particle-size translation combines units, statistical percentiles, test methods and directional language. The broader method is developed in Master Art of Translation | The Complete System for Moving Meaning Between Languages. Vocabulary depth connects to the Vocabulary Learning Hub, while comparison, distribution and threshold language connect to How English Works.
FAQ
Is mesh the same as microns?
No. Mesh is a sieve designation within a defined system; micrometres are a physical unit of length.
Does higher mesh mean larger particles?
Usually the opposite: higher mesh numbers generally correspond to finer openings within a given sieve system.
Is D50 the average particle size?
Not necessarily. It is commonly the median percentile of the reported distribution.
Is D90 the maximum size?
No. It marks a percentile, leaving a portion of the distribution above that size.
Can mesh always be converted to microns?
You can map a sieve number to a nominal aperture when the applicable standard is known. It is not a universal one-to-one conversion independent of standard.
Do laser diffraction and sieving measure the same thing?
They characterize particle size through different physical methods and can produce different representations.
Why does distribution basis matter?
Number-, mass- and volume-weighted distributions give different influence to different particle sizes.
Should passing and retained be translated literally?
Use established laboratory terminology in the target language, but preserve the direction exactly.
Can AI choose a mesh conversion table?
It can assist, but the governing sieve standard must be specified and verified independently.
What is the simplest rule?
Protect the measurement method, unit, percentile or sieve direction before translating the descriptive language.
Final checklist
- Is the quantity physical diameter, mesh, sieve aperture or percentile size?
- Are nm, µm and mm prefixes preserved?
- Is the sieve or mesh standard known where required?
- Are passing and retained directions correct?
- Are D10, D50 and D90 kept as percentiles?
- Is the distribution basis—number, volume or mass—preserved?
- Is the test method retained?
- Are range, minimum and maximum statements kept distinct?
- Are agglomerates and primary particles distinguished?
- Would the target specification describe the same particle population as the source?
Particle-size translation succeeds when the target reader sees the same distribution, the same sieve direction and the same analytical method as the source reader. Protect units and mesh conventions, preserve percentile meaning, keep retained and passing fractions straight, and treat conversions as method-specific technical mappings rather than simple word substitutions.
Advanced translation lab: particle-size decisions that depend on more than a diameter
Particle-size work becomes difficult when a target reader assumes that every number describes the same geometry. In practice, the source may define a sieve aperture, a statistical percentile, a hydrodynamic diameter, an aerodynamic diameter, a Feret diameter or a commercial grade. Translation must preserve the measurement model as well as the number. The safest question is not “What does this size equal?” but “What exactly was measured, by which method, and what decision is this value meant to support?”
Case 1: procurement specification versus laboratory result
A purchase specification may require “D90 ≤ 75 µm,” while the supplier certificate reports “D90 62 µm.” The first is an acceptance limit; the second is a measured result. Translate maximum, result, lot, method and conformance language separately. If the target compresses both lines into “particle size 62–75 µm,” it creates a false range and destroys the pass/fail structure.
Case 2: sieve grade versus laser-diffraction percentile
A powder may be sold as “−200 mesh” while a laboratory report gives D50 and D90 by laser diffraction. These descriptions can coexist because they come from different methods. A translation should not use the laser D50 to redefine the commercial mesh grade, nor should it turn the mesh grade into a claim that every particle is smaller than one exact diameter.
Case 3: distribution basis changes the apparent size
Imagine one report gives a number-weighted median and another gives a volume-weighted median for the same sample. A small number of large particles can strongly affect the volume distribution while barely changing the number distribution. Translating both simply as “median particle size” removes the basis that explains why the values differ. Preserve whether the statistic is number-, mass- or volume-weighted whenever the source supplies that information.
Case 4: irregular particles and equivalent diameters
Fibres, flakes and crushed minerals do not have one obvious diameter. Image-analysis software may report equivalent circular diameter, Feret maximum, Feret minimum or aspect ratio. A translation that shortens these to “diameter” falsely suggests spherical geometry. Preserve the descriptor and, where needed, explain in target-language prose that it is an equivalent or projected measurement rather than a literal physical width in every direction.
Case 5: agglomerates versus primary particles
Nanopowders and pigments can contain primary particles that cluster into much larger agglomerates. Electron microscopy may report primary-particle dimensions while laser diffraction measures dispersed or partially dispersed clusters. Keep primary, aggregate and agglomerate terminology exact. If the source describes dispersion conditions, sonication or dispersant use, retain them because they can explain apparently contradictory size results.
Case 6: wet versus dry measurement
Some instruments measure particles suspended in liquid; others use dry dispersion. The sample can break apart, swell, dissolve or agglomerate differently under those conditions. Translate “wet method,” “dry method,” carrier liquid, dispersion pressure and sample-preparation language rather than presenting all readings as directly interchangeable measurements of the same state.
Case 7: filter claims and capture efficiency
A “10 µm filter” may be nominal, absolute or tied to an efficiency curve. Particle size alone does not describe capture probability. Translate nominal rating, absolute rating, efficiency percentage and test-particle information as separate fields. Otherwise a target reader may interpret a nominal rating as a guarantee that every particle above the stated size is captured.
Case 8: pharmaceutical and food cut sizes
Specifications for active ingredients, excipients, flour, sugar or spices may use upper and lower sieve limits to control flow, dissolution, texture or processing. Translate each cut point together with passing or retained percentage. Do not replace a two-sieve grading specification with a single average size, because the distribution width may be exactly what controls product performance.
Case 9: cumulative versus differential plots
Particle reports often include both a differential distribution, showing how much material occurs around each size, and a cumulative curve, showing how much lies below a size. Translate axis titles, percentages and legends so readers know which curve they are looking at. A peak on a differential curve is not the same thing as a cumulative D50.
Case 10: specification language around oversize contamination
A powder may have a normal D90 well below 100 µm while the specification separately limits oversize contamination above 250 µm. The large-particle limit is not redundant. Preserve phrases such as “no particles above,” “maximum retained,” “trace oversize” or “foreign material” according to the source. These statements can control quality risks that percentile statistics do not reveal.
Case 11: decimal precision and instrument output
An instrument might report D50 = 24.7 µm, while a product catalogue rounds the same material family to “approximately 25 µm.” Preserve the precision appropriate to each document. Do not inflate a marketing number to laboratory precision or round a certificate result merely to make target-language tables look cleaner.
Case 12: cross-document terminology control
One organization may use “particle size distribution,” “granulometry,” “PSD,” “grading” and “sieve analysis” across different departments. A translator should build a small concept map rather than force every term into one phrase. Standardize genuine synonyms where appropriate, but preserve method-specific distinctions when one document refers to a test procedure and another to the resulting distribution.
A final decision rule for particle-size translation
Before releasing a translated particle-size statement, ask: What physical or statistical quantity does this number represent? Which method produced it? Is the distribution based on number, mass or volume? Does the statement describe a result, an acceptance limit or a commercial grade? And would the target reader select or reject the same material as the source reader? If those answers remain unchanged, the translation has preserved the size information that actually matters.