Sieve Aperture Calculator
Nominal apertures and the three E11/ISO tolerances for every standard sieve.
Calculator
ASTM E11 Table 1 — tolerances
- Nominal aperture
- 125,000 µm · 125 mm
- Permissible variation of average aperture (±Y)
- ± 3,700 µm
- Opening not to be exceeded by more than 5% of openings (X)
- 130,000 µm
- Maximum individual opening
- 130,900 µm
- Nominal wire diameter
- 8 mm
- Alternative designation (USA)
- 5 in.
- ISO 565 series
- R20/3
Values read directly from ASTM E11-95 Table 1 — never derived by formula.
Theory & method
Every test sieve designation in ASTM E11 (harmonized with ISO 565 and ISO 3310-1) corresponds to a nominal aperture — the target opening of the woven wire cloth — plus tolerance limits that define how much real openings may deviate. These values are published in Table 1 of the standard; they are measured specifications, not the result of a formula. A widespread shortcut, aperture = 25,400/mesh, is wrong because it ignores the wire diameter: it computes the mesh pitch, not the opening.
Table 1 defines three tolerance figures per sieve. The permissible variation of average aperture (±Y) bounds the mean of all openings; the value X is the opening size not to be exceeded by more than 5% of the openings; and the maximum individual opening caps any single opening in the cloth. For example, a 850 µm (No. 20) sieve allows an average within ±35 µm, at most 5% of openings above 925 µm, and no opening above 970 µm.
These three limits are what separate a compliance-grade sieve from a worn or defective one, and they are the basis of the verification levels of ISO 3310-1 (compliance, inspection and calibration grades). When an aperture you enter does not match any standard designation, this calculator shows the nearest standard sieves instead of inventing tolerances for a sieve that does not exist.
How to use
- 01Pick a sieve designation from the ASTM E11 Table 1 list — standard (ISO) and alternative (USA) designations are shown together.
- 02Or type an aperture in µm: an exact match shows that sieve; any other value shows the nearest standard sieve and its neighbors.
- 03Read the nominal aperture, the three Table 1 tolerances (±Y, X, maximum individual opening) and the nominal wire diameter.
- 04Check the ISO 565 series tag: R20/3 (principal) or R40/3 (supplementary); sieves marked as common usage are E11 footnote D items outside the standard series.
Frequently asked questions
Why can't the aperture be computed as 25,400/mesh?
Because mesh count includes the wire: 25,400/mesh gives the pitch (opening + wire diameter), not the opening. A No. 20 sieve would come out as 1,270 µm when the real nominal aperture is 850 µm. Apertures and tolerances must be read from ASTM E11 Table 1.
What do the three tolerance values mean?
The average-aperture variation (±Y) limits the mean of all openings; X is the size that no more than 5% of openings may exceed; the maximum individual opening is an absolute cap on any single opening. Columns 5 and 6 are absolute opening sizes, not deltas.
What is the difference between R20/3 and R40/3 series?
They are Renard series from ISO 565: R20/3 is the principal series (each aperture ~2× the previous within the series) and R40/3 is the supplementary series that fills intermediate sizes. Sieves with no series tag are US common-usage sizes listed in E11 footnote D.
Which sieve should I use for an arbitrary particle size?
Sieves only exist in the normative designations. For a size between two standard apertures, use the neighboring sieves shown by the calculator — the finer one retains the size of interest and the coarser one passes it.
Normative references
- ASTM E11-95 — Standard Specification for Wire-Cloth Sieves for Testing Purposes, Table 1.
- ISO 565:1990 — Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of openings.
- ISO 3310-1:2016 — Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth.