Exact and reverse lookup
Sieve Size Lookup and Conversion
Find an exact designation or the immediately coarser and finer included openings.
Default reference: A No. 4 sieve has a nominal opening of 4.75 mm, 4,750 µm, or approximately 0.1870 in. Use the table below for the complete no-JavaScript reference.
Exact standard sieve
Adjacent included sieve openings
No. 4 has a nominal clear opening of 4,750 µm.
Nominal reference
Mesh number is not a universal length conversion. The clear opening depends on the defined sieve series and wire cloth. Verify the governing test method, current standard, and certified sieve condition before acceptance testing.
Nominal opening reference
U.S. Sieve Sizes and Nominal Openings
SI opening values control; inches are calculated informational conversions.
Search any designation or opening. Select a column heading to sort after JavaScript loads.
No included sieve matches that search. Try a designation such as No. 40, or use opening lookup to find the bracketing standard sizes.
Scroll horizontally to view additional columns and vertically to view additional rows. Column headers remain visible while scrolling.
| U.S. alternative designation | Nominal aperture | |||
|---|---|---|---|---|
| 25.0 mm | 1 in. | 25.0 | 25,000 | 0.9843 |
| 19.0 mm | 3/4 in. | 19.0 | 19,000 | 0.7480 |
| 12.5 mm | 1/2 in. | 12.5 | 12,500 | 0.4921 |
| 9.5 mm | 3/8 in. | 9.5 | 9,500 | 0.3740 |
| 6.3 mm | 1/4 in. | 6.3 | 6,300 | 0.2480 |
| 4.75 mm | No. 4 | 4.75 | 4,750 | 0.1870 |
| 4.00 mm | No. 5 | 4.00 | 4,000 | 0.1575 |
| 3.35 mm | No. 6 | 3.35 | 3,350 | 0.1319 |
| 2.80 mm | No. 7 | 2.80 | 2,800 | 0.1102 |
| 2.36 mm | No. 8 | 2.36 | 2,360 | 0.09291 |
| 2.00 mm | No. 10 | 2.00 | 2,000 | 0.07874 |
| 1.70 mm | No. 12 | 1.70 | 1,700 | 0.06693 |
| 1.40 mm | No. 14 | 1.40 | 1,400 | 0.05512 |
| 1.18 mm | No. 16 | 1.18 | 1,180 | 0.04646 |
| 1.00 mm | No. 18 | 1.00 | 1,000 | 0.03937 |
| 850 µm | No. 20 | 0.850 | 850 | 0.03346 |
| 710 µm | No. 25 | 0.710 | 710 | 0.02795 |
| 600 µm | No. 30 | 0.600 | 600 | 0.02362 |
| 500 µm | No. 35 | 0.500 | 500 | 0.01969 |
| 425 µm | No. 40 | 0.425 | 425 | 0.01673 |
| 355 µm | No. 45 | 0.355 | 355 | 0.01398 |
| 300 µm | No. 50 | 0.300 | 300 | 0.01181 |
| 250 µm | No. 60 | 0.250 | 250 | 0.009843 |
| 212 µm | No. 70 | 0.212 | 212 | 0.008346 |
| 180 µm | No. 80 | 0.180 | 180 | 0.007087 |
| 150 µm | No. 100 | 0.150 | 150 | 0.005906 |
| 125 µm | No. 120 | 0.125 | 125 | 0.004921 |
| 106 µm | No. 140 | 0.106 | 106 | 0.004173 |
| 90 µm | No. 170 | 0.090 | 90 | 0.003543 |
| 75 µm | No. 200 | 0.075 | 75 | 0.002953 |
| 63 µm | No. 230 | 0.063 | 63 | 0.002480 |
| 53 µm | No. 270 | 0.053 | 53 | 0.002087 |
| 45 µm | No. 325 | 0.045 | 45 | 0.001772 |
| 38 µm | No. 400 | 0.038 | 38 | 0.001496 |
Nominal opening is not a measured particle-diameter guarantee or a substitute for sieve tolerances, certification, condition checks, or the governing material test method.
Filter designation type
How to Use the Sieve Size Chart
- Choose a lookup mode. Use designation mode for entries such as No. 40 or 3/8 in. Use opening mode for a numeric target.
- Enter the value and unit. Opening lookup converts mm, µm, or inches to canonical micrometers before matching.
- Read the result. An exact opening returns one row. A nonstandard value returns the immediately coarser and finer included rows plus the proportionally nearest opening.
- Confirm the application. Copy or print the reference, then verify the controlling test method and current standard before substituting or accepting a sieve.
The full table remains the primary reference. Search and filters change only which rows are visible; they do not change any engineering value.
Mesh, Aperture, and Pass/Retain Notation
What sieve number and nominal opening mean
The nominal opening is the clear square aperture between wires. Mesh count is a designation related to openings per linear inch, but the wire occupies part of that inch. The useful relationship is pitch = clear opening + wire diameter; because wire diameter varies with the defined cloth, a formula such as 25,400 ÷ mesh does not produce a reliable ASTM opening in micrometers.
Passing and retained notation
| Notation | Typical meaning | Interpretation |
|---|---|---|
| −40 | Passing No. 40 | Material that passes the nominal 425 µm opening under the stated procedure. |
| +40 | Retained on No. 40 | Material retained by the sieve under the stated procedure. |
| −4 +40 | Pass No. 4; retain No. 40 | A nominal fraction between 4.75 mm and 425 µm. |
These boundaries are nominal. Elongated particles may orient through an opening; flat particles, agglomerates, loading, blinding, damage, and test duration can also affect the observed fraction.
ASTM and ISO designations are not interchangeable labels
ASTM E11 covers woven-wire test sieve cloth and test sieves with nominal apertures from 125 mm to 20 µm, with SI values standard for sieve-cloth openings. ISO 3310-1 covers metal-wire-cloth test sieves across a similar aperture range. Many nominal apertures align, but users must still check the governing standard, designation, tolerances, available series, frame requirements, and test method. This page does not reproduce those controlled requirements.
Worked Sieve Lookup Examples
Find a sieve near a 0.10 mm target
Convert: 0.10 mm × 1,000 = 100 µm.
Bracket: The adjacent included openings are 106 µm (No. 140) and 90 µm (No. 170).
Compare proportionally: |ln(106/100)| is smaller than |ln(90/100)|, so No. 140 is nearer by opening ratio.
Limit: “Nearer” does not permit substitution when a procedure specifies a particular sieve.
Interpret No. 4 and No. 200 in soil testing
No. 4 corresponds to a 4.75 mm nominal opening, while No. 200 corresponds to 75 µm. In common U.S. geotechnical context, these sieves help separate gravel, sand, and fines fractions and report percent passing.
Those boundaries are application-specific rather than universal classifications for powders, food, mining products, or manufactured particles. Follow the named soil test and classification procedure.
Common Sieve Selection and Testing Mistakes
Using one mesh formula
Mesh count alone omits wire diameter. Use a verified designation-to-opening row rather than calculating aperture from count.
Confusing aperture and frame diameter
A 200 mm or 8 in. sieve frame describes the frame, not the clear wire-cloth opening.
Substituting the nearest size
The nearest nominal opening is a selection aid only. A specified test may require an exact sieve and sequence.
Ignoring sieve condition
Damaged, distorted, worn, overloaded, or plugged cloth can change the effective separation even when the label is correct.
Mixing wet and dry procedures
Dispersion, washing, drying, duration, and agitation can change results. Match the prescribed procedure.
Treating retained particles as one size
A retained fraction spans a range and is affected by particle shape and orientation; it is not a set of particles equal to the opening.
Sources, Scope, and Data Limitations
Selected nominal-opening reference for common U.S. sieve designations; not a reproduction of a complete standard.
ASTM E11-24 is the controlling basis for current U.S. woven-wire test-sieve requirements. The table publishes only an independently selected set of nominal designation/opening facts needed for lookup. Inch values are calculated from canonical SI openings using the exact relationship 1 in. = 25.4 mm.
- ASTM E11-24 — Standard Specification for Woven Wire Test Sieve Cloth and Test SievesControls current scope, terminology, nominal aperture range, and test-sieve requirements. Purchase or licensed access is required for the complete standard.
- ISO 3310-1:2016 — Test sieves of metal wire clothUsed only to explain ISO scope and why standards must not be mixed silently.
- NIST Guide to the SI, Appendix BSupports exact inch-to-millimeter conversion and converted-value rounding.
- FHWA Geotechnical Aspects of Pavements, Chapter 5Supports geotechnical percent-passing context and common No. 4 and No. 200 application boundaries.
- Arizona DOT Metric Guide, Appendix A2, Table 6Public-agency corroboration for the selected standard and alternate nominal sieve designations.
Dataset and Source-Check Details
- Dataset
- Selected common U.S. sieve designations and nominal openings
- Canonical unit
- Integer micrometers
- Calculated fields
- Millimeters by ÷ 1,000; inches by ÷ 25,400
- Included range
- 25.0 mm through 38 µm
- Excluded
- Tolerances, wire diameters, sampling, confidence classes, certification, and frame construction
- Downloads
- Bulk CSV disabled because the controlling standards are copyrighted
- Source check
- August 9, 2026; selected nominal values and cited source scope
- Publisher
- Turn2Engineering
Sieve Size Chart FAQ
A No. 4 sieve has a nominal opening of 4.75 mm, or 4,750 µm. The informational inch conversion is approximately 0.1870 in.
Micrometers directly express nominal clear-opening length. Mesh is a sieve or wire-cloth designation related to opening count and wire diameter, so it is not itself a length unit.
No. Dividing 25,400 by mesh count estimates pitch, not clear aperture, because it does not subtract wire diameter. Use a verified sieve designation table.
Minus generally means material passing the named sieve, while plus means material retained on it. Always confirm the convention in the test method or supplier specification.
Many nominal apertures align, but the standards, designations, tolerances, available sizes, frames, and governing requirements must still be checked separately.
Use Nominal Openings as a Reference, Not a Certification
Use the lookup to resolve a designation, convert its nominal opening, or bracket a target. For laboratory acceptance, procurement, or compliance, verify the current ASTM or ISO standard, the named material test method, and the actual sieve’s certification and condition.