The right mesh depends on the job. Here are typical mesh counts and micron openings for common screens, strainers, filters and test sieves.
| Application | Typical spec | What the numbers are |
|---|---|---|
| Flour milling | No. 70 sieve (212 µm) — at least 98% must pass | Opening |
| Pharmaceutical powder fineness | x50 class limits: 125 · 180 · 355 µm | Particle size — not a screen spec |
| Homebrew hop spiders & filters | 300 µm stainless mesh (as sold) | Opening |
| Coffee grind sifting | Sieves from 200 to 1600 µm | Opening range |
| Drip irrigation filters | At least 120 mesh; drip tape at least 155 mesh | Minimum mesh |
| Sprayer nozzle tip strainers | 24, 50, 80, 100 or 200 mesh | Mesh count |
| Airless paint sprayer gun filters | 60 mesh latex · 100 mesh stain/lacquer | Mesh count |
| Paint strainers | Medium 260 µm · fine 190 µm · extra-fine 125 µm | Opening |
| Hydraulic pump suction strainers | 100 mesh (≈ 150 µm); 60 mesh (≈ 240 µm) suggested | Mesh count + Opening |
| Pipeline Y-strainers | Water 20–40 mesh · steam 40–60 mesh | Mesh count range |
| Whole-house spin-down sediment filters | 60 mesh (254 µm) · 100 (152 µm) · 140 (104 µm) | Mesh count + Opening |
| Fuel pump pre-filters | 100 µm in-tank strainer; 70–100 µm pre-pump | Opening range |
| Concrete sand grading (ASTM C33) | No. 4, 8, 16, 30, 50, 100 sieves | Opening |
| Soil classification (USCS) | No. 4 (gravel/sand) · No. 200 (fines) | Opening |
| Mineral flotation grinding | Example: ≈ 70% passing 200 mesh (75 µm) | Particle size — not a screen spec |
| Metal 3D printing powders | Powder cuts: LPBF 20–53 µm · EBM 45–106 µm | Particle size — not a screen spec |
| Drilling shale shaker screens | API 20 – API 325 (tested separation) | Tested separation — not an opening |
| Screen printing (polyester mesh) | 110 · 156 · 230 · 305 threads per inch | Mesh count |
| Window & door insect screens | 18×16 standard · 20×20 no-see-um | Mesh count (two directions) |
| Micro-mesh gutter guards | e.g. 42 mesh stainless, ≈ 440 µm | Opening |
| Rodent-proof hardware cloth | ¼" for mice · ½" for rats | Trade size (nominal) |
| Compost & soil sifting | ¼" for seed mix · ½" coarse | Trade size (nominal) |
| Beehive screened bottom boards | #8 hardware cloth (8 per inch) | Mesh count |
| Gold prospecting classifiers | ½", ¼", ⅛" then finer | Trade size (nominal) |
| Plankton sampling nets | Standard: phyto 55 µm · zoo 335 µm (custom 10–780 µm) | Opening |
At least 120 mesh; drip tape at least 155 mesh
Drip line, emitters and sprayers need at least 120 mesh filtration; drip tape needs at least 155 mesh. Follow the emitter maker for your water quality.
24, 50, 80, 100 or 200 mesh
Agricultural nozzle tip strainers are offered with stainless screens of 24, 50, 80, 100 or 200 mesh to keep spray tips from plugging.
Sources: TeeJet strainers catalog
60 mesh latex · 100 mesh stain/lacquer
Use 60 mesh for primer and latex paint, 100 mesh for thinner materials such as stain and lacquer.
Sources: Graco — Gun filters, 60 and 100 mesh
Medium 260 µm · fine 190 µm · extra-fine 125 µm
Cone paint strainers are sold as medium (260 µm) and fine (190 µm); extra-fine 125 µm strainers are also available.
Sources: TotalBoat — Paint strainers · TCP Global — Auto paint strainers (125 µm) — see 120 mesh
100 mesh (≈ 150 µm); 60 mesh (≈ 240 µm) suggested
Pump inlet strainers are commonly 100 mesh (≈ 150 µm); one engineering recommendation is 60 mesh (≈ 240 µm) where a suction strainer is used, to lower cavitation risk.
Sources: Machinery Lubrication — Suction line filtration — see 100 mesh
Water 20–40 mesh · steam 40–60 mesh
A common recommendation: 20–40 mesh for chilled and city water lines, 40–60 mesh for steam (very fine mesh is eroded by high-velocity steam). Follow the equipment maker for your service.
Sources: TOT Valve — Y-strainer mesh size guide · Union Valve — Y strainer mesh selection
60 mesh (254 µm) · 100 (152 µm) · 140 (104 µm)
Replacement screens are offered at 60 mesh (254 µm) and finer options such as 100 mesh (152 µm) and 140 mesh (104 µm); pick the coarsest screen that catches your sediment, since finer screens clog faster.
Sources: Fresh Water Systems — Rusco spin-down screens · Rusco — FAQ
100 µm in-tank strainer; 70–100 µm pre-pump
In-tank stainless strainers rated 100 µm protect the pump from debris; guidance for pre-pump filtration on carbureted systems is about 70–100 µm. Injector protection needs a finer post-pump filter.
Sources: FUELAB — 100 micron in-tank straining filter · Speedway Motors — Fuel filter micron ratings
No. 4, 8, 16, 30, 50, 100 sieves
ASTM C33/C33M-23 grades fine aggregate on the No. 4 to No. 100 sieves: 95–100% passing No. 4 (4.75 mm) and 0–10% passing No. 100 (150 µm).
Sources: ASTM C33/C33M-23 (preview) — see 100 mesh, 50 mesh, 30 mesh, 16 mesh, 8 mesh, 4 mesh
No. 4 (gravel/sand) · No. 200 (fines)
ASTM D2487 uses the No. 4 sieve (4.75 mm) to separate gravel from sand and the No. 200 sieve (75 µm) to define fines.
Sources: ASTM D2487 — Classification of soils (USCS) · Unified Soil Classification System — see 200 mesh, 4 mesh
No. 70 sieve (212 µm) — at least 98% must pass
US standard of identity: at least 98% of "flour" must pass a woven wire cloth no coarser than 212 µm (No. 70). This is a regulatory limit, not the only sieve a mill may use.
Sources: 21 CFR 137.105 — Flour (eCFR) — see 70 mesh
x50 class limits: 125 · 180 · 355 µm
USP <811> (harmonized text, official 2012) classes powders by median particle size x50: coarse > 355 µm, moderately fine 180–355 µm, fine 125–180 µm, very fine ≤ 125 µm. These are particle-size limits, not screen openings.
300 µm stainless mesh (as sold)
Hop spiders are sold with 300 µm stainless mesh. Forum users brewing heavily hopped beers report that 300 µm can clog and prefer coarser mesh.
Sources: Homebrew Finds — 300 micron hop spider (product listing) · Homebrew Talk — which mesh size for hop spider (forum) — see 50 mesh
Sieves from 200 to 1600 µm
Coffee sifters stack interchangeable sieves between 200 and 1600 µm to isolate a target grind range.
Sources: KRUVE Sifter Plus — sieve sizes
Example: ≈ 70% passing 200 mesh (75 µm)
Grind size is a particle size, not a screen spec. One described copper circuit grinds to about 70% minus 200 mesh (75 µm); the right target for any ore is set by test work.
Powder cuts: LPBF 20–53 µm · EBM 45–106 µm
A Ti-6Al-4V study compares the usual laser powder bed fusion cut (20–53 µm) with the coarser 45–106 µm cut associated with electron beam melting. These are powder sizes, not screen openings.
Sources: Materials (PMC) — Ti-6Al-4V powder size distributions for PBF-LB/M
API 20 – API 325 (tested separation)
API RP 13C labels shaker screens by tested separation size, not wire count or geometric opening, so an "API 100" screen is not the same as 100 mesh cloth. A supplier table puts API 20 at about 833 µm and API 325 at about 44 µm.
110 · 156 · 230 · 305 threads per inch
Screen printing mesh is polyester, counted in threads per inch: 110 and 156 are the common general-purpose counts; 230 and 305 hold finer detail. Not comparable to metal sieve openings.
Sources: ScreenPrinting.com — Mesh size guide
18×16 standard · 20×20 no-see-um
Sold as 18×16 mesh (18 and 16 openings per inch in the two directions) for standard residential screens, and 20×20 "no-see-um" mesh for smaller biting insects.
Sources: Phifer 18×16 standard mesh · Phifer 20×20 no-see-um mesh
e.g. 42 mesh stainless, ≈ 440 µm
Stainless micro-mesh gutter guards pass water by surface tension and hold back debris; one maker specifies 42-mesh stainless with about 440 µm openings.
Sources: Leaf Solution — micro-mesh specs
¼" for mice · ½" for rats
Hardware cloth is sold by nominal opening size in fractions of an inch: ¼" is recommended to exclude mice and ½" for rats. A ¼" trade size is not the same thing as an ASTM No. 4 sieve (4.75 mm).
Sources: Extension — Rodent exclusion methods · Howard Wire — Hardware cloth sizes
¼" for seed mix · ½" coarse
Gardeners commonly sift seed-starting and potting mix through ¼" hardware cloth and use ½" for a first coarse pass.
Sources: How to screen soil — mesh sizes
#8 hardware cloth (8 per inch)
#8 hardware cloth (8 openings per inch) lets Varroa mites that drop off bees fall out of the hive while keeping bees in.
Sources: NC State Extension — Managing Varroa mites · Honey Bee Suite — hardware cloth for hives
½", ¼", ⅛" then finer
Prospectors screen material in steps — ½", ¼", ⅛" — before panning. Finer classifiers are often named by opening as a fraction of an inch (e.g. "#20" ≈ 1/20"), which is not the same as ASTM No. 20.
Sources: GPAA — What classifier sizes · ASR Outdoor — Classifier mesh sizes
Standard: phyto 55 µm · zoo 335 µm (custom 10–780 µm)
A standard Apstein net uses 55 µm mesh for phytoplankton and 335 µm for zooplankton; custom meshes from 10 to 780 µm are available. Mesh choice depends on the target organisms.
Sources: Hydro-Bios — Apstein plankton net manual · Univ. of Tasmania — Zooplankton sampling
Standard residential insect screen is 18×16 mesh. Finer 20×20 "no-see-um" mesh is used where gnats and midges are a problem.
It depends on what you are protecting: pipeline Y-strainers for water are usually 20–40 mesh, hydraulic pump suction strainers 100 mesh (≈150 µm), and drip irrigation filters at least 120 mesh.
Each entry lists its sources and is labelled with the kind of evidence behind it — regulation, standard, maker spec, product listings, industry guide, research or common practice. We keep the kind of number the source gives — a screen opening, a mesh count, a minimum mesh, counts in two directions, a fractional-inch trade size, or a particle size — and never convert one into another. Only screen openings and single-direction mesh counts are used to suggest applications in the calculator. Paired counts such as 18×16 are shown for reference because one mesh number cannot establish both directions. Ranges show common practice, not hard limits — always check the equipment maker’s recommendation.