U.S. sieve number to opening size
U.S. Sieve Size Chart — mm, Microns & Inches
Use the search box for the fastest match, or scan the table from coarse to fine.
Fast lookup: search No. 40, #40, 40 mesh, 425 microns, 0.425 mm, or 0.01673 in. All refer to the same nominal opening row in this chart.
Common sieve sizes
Quick Reference
Popular U.S. sieve numbers frequently used in soil, aggregate, and particle-size work.
No sieve size matches that search. Try a designation such as No. 40 or an opening such as 425 microns.
Scroll horizontally to view all opening-unit columns and vertically to view additional sieve sizes. The sieve designation column and headers remain visible while scrolling.
| Opening (mm) | Opening (µm) | Opening (in) | Copy | |
|---|---|---|---|---|
| 4 in. | 100.0 | 100,000 | 3.9370 | |
| 3 1/2 in. | 90.0 | 90,000 | 3.5433 | |
| 3 in. | 75.0 | 75,000 | 2.9528 | |
| 2 1/2 in. | 63.0 | 63,000 | 2.4803 | |
| 2.12 in. | 53.0 | 53,000 | 2.0866 | |
| 2 in. | 50.0 | 50,000 | 1.9685 | |
| 1 3/4 in. | 45.0 | 45,000 | 1.7717 | |
| 1 1/2 in. | 37.5 | 37,500 | 1.4764 | |
| 1 1/4 in. | 31.5 | 31,500 | 1.2402 | |
| 1.06 in. | 26.5 | 26,500 | 1.0433 | |
| 1 in. | 25.0 | 25,000 | 0.9843 | |
| 7/8 in. | 22.4 | 22,400 | 0.8819 | |
| 3/4 in. | 19.0 | 19,000 | 0.7480 | |
| 5/8 in. | 16.0 | 16,000 | 0.6299 | |
| 0.530 in. | 13.2 | 13,200 | 0.5197 | |
| 1/2 in. | 12.5 | 12,500 | 0.4921 | |
| 7/16 in. | 11.2 | 11,200 | 0.4409 | |
| 3/8 in. | 9.50 | 9,500 | 0.3740 | |
| 5/16 in. | 8.00 | 8,000 | 0.3150 | |
| 0.265 in. | 6.70 | 6,700 | 0.2638 | |
| 1/4 in. | 6.30 | 6,300 | 0.2480 | |
| No. 3-1/2 | 5.60 | 5,600 | 0.2205 | |
| No. 4 | 4.75 | 4,750 | 0.1870 | |
| No. 5 | 4.00 | 4,000 | 0.1575 | |
| No. 6 | 3.35 | 3,350 | 0.1319 | |
| No. 7 | 2.80 | 2,800 | 0.1102 | |
| No. 8 | 2.36 | 2,360 | 0.0929 | |
| No. 10 | 2.00 | 2,000 | 0.0787 | |
| No. 12 | 1.70 | 1,700 | 0.0669 | |
| No. 14 | 1.40 | 1,400 | 0.0551 | |
| No. 16 | 1.18 | 1,180 | 0.0465 | |
| No. 18 | 1.00 | 1,000 | 0.0394 | |
| No. 20 | 0.850 | 850 | 0.033465 | |
| No. 25 | 0.710 | 710 | 0.027953 | |
| No. 30 | 0.600 | 600 | 0.023622 | |
| No. 35 | 0.500 | 500 | 0.019685 | |
| No. 40 | 0.425 | 425 | 0.016732 | |
| No. 45 | 0.355 | 355 | 0.013976 | |
| No. 50 | 0.300 | 300 | 0.011811 | |
| No. 60 | 0.250 | 250 | 0.009843 | |
| No. 70 | 0.212 | 212 | 0.008346 | |
| No. 80 | 0.180 | 180 | 0.007087 | |
| No. 100 | 0.150 | 150 | 0.005906 | |
| No. 120 | 0.125 | 125 | 0.004921 | |
| No. 140 | 0.106 | 106 | 0.004173 | |
| No. 170 | 0.090 | 90 | 0.003543 | |
| No. 200 | 0.075 | 75 | 0.002953 | |
| No. 230 | 0.063 | 63 | 0.002480 | |
| No. 270 | 0.053 | 53 | 0.002087 | |
| No. 325 | 0.045 | 45 | 0.001772 | |
| No. 400 | 0.038 | 38 | 0.001496 | |
| No. 450 | 0.032 | 32 | 0.001260 | |
| No. 500 | 0.025 | 25 | 0.000984 | |
| No. 635 | 0.020 | 20 | 0.000787 |
Important: sieve number is a designation, not a universal length formula. Nominal opening depends on the defined sieve series and wire cloth. Use the governing test method and current sieve specification for acceptance work.
Sieve Size Chart — U.S. sieve designations with nominal opening conversions in millimeters, micrometers, and inches. Verify the governing test method and current sieve specification before acceptance testing.
Common Sieve Sizes and What They Mean
A common coarse/fine boundary in U.S. soil and aggregate work. In geotechnical classification, it is frequently used to separate gravel-size from sand-size material.
Common in soil and aggregate gradation work and one of the sieve sizes used in AASHTO soil-classification inputs.
Widely used in geotechnical testing. The fraction passing No. 40 is also the material used for Atterberg-limit preparation in common soil-test workflows.
A key fines boundary in U.S. soil and aggregate testing. Material passing this sieve is commonly reported as the fines fraction.
Application matters
A familiar sieve number does not create the same classification rule in every industry. Soil, aggregate, powder, food, mineral, and manufacturing specifications may use the same opening for different purposes.
How to Read a Sieve Size Chart
- Start with the designation you know. Enter No. 40, #40, 40 mesh, an opening in mm, or an opening in microns.
- Read across the row. The millimeter, micrometer, and inch columns are different unit expressions of the same nominal clear opening.
- Keep coarse-to-fine direction straight. Larger openings are coarser. As the numbered U.S. sieve designation increases, the nominal opening generally becomes smaller.
- Use the chart as a reference, not a tolerance certificate. Acceptance testing still depends on the specified sieve standard, test method, sieve condition, and any required inspection or calibration class.
Passing and retained notation
| Notation | Typical meaning | Example |
|---|---|---|
| −40 | Passing No. 40 | Material that passes the nominal 425 µm opening under the stated procedure. |
| +40 | Retained on No. 40 | Material retained on the No. 40 sieve under the stated procedure. |
| −4 +40 | Pass No. 4; retain No. 40 | A nominal size fraction between 4.75 mm and 425 µm. |
Mesh Size vs. Microns: Why There Is No Single Formula
The sieve opening is the clear space between adjacent wires. A mesh-style number is related to the wire-cloth pattern, but the wire itself occupies part of each pitch. That is why simply dividing 25,400 µm by a mesh count does not reproduce the standardized clear opening.
Use a verified designation-to-opening chart when converting a U.S. sieve number to microns or millimeters. The search above accepts common “mesh” phrasing because that is how many users describe numbered sieves, but the displayed opening is the value that should be used for dimensional comparison.
Sieve number
A standardized designation for a defined test-sieve opening series.
Nominal opening
The clear aperture size, expressed directly in mm or µm.
Frame diameter
The physical sieve frame size, such as 8 in. or 200 mm; it is not the mesh opening.
Particle size
A material characteristic inferred from passage/retention behavior; it is not guaranteed to equal the opening dimension for every particle shape.
Sieve Standards, Sources, and Scope
This page is an independent lookup and unit-conversion reference, not a reproduction of a complete ASTM or ISO standard.
ASTM E11-24 is the active ASTM specification for woven-wire test sieve cloth and test sieves. ASTM states that SI values are standard for sieve-cloth openings and wire diameters, and that the specification covers nominal apertures from 125 mm down to 20 µm. ISO 3310-1:2016 remains current and covers metal-wire-cloth test sieves over the same aperture range in accordance with ISO 565.
- ASTM E11-24 — Standard Specification for Woven Wire Test Sieve Cloth and Test SievesPrimary U.S. specification for sieve cloth, test-sieve construction, inspection, and nominal aperture scope.
- ISO 3310-1:2016 — Test sieves of metal wire clothCurrent ISO technical requirements and testing reference for wire-cloth test sieves.
- Gilson — U.S. and Metric Sieve SizesPublic industry reference used to corroborate common U.S. alternative designations and nominal opening mappings.
- NIST Guide to the SI, Appendix BSupports exact inch-to-millimeter conversion used for the informational inch column.
Dataset and Source-Check Details
- Dataset
- U.S. alternative sieve designations and nominal openings from 4 in. through No. 635
- Canonical unit
- Millimeters / micrometers
- Calculated field
- Inches using 1 in. = 25.4 mm
- Included range
- 100 mm through 20 µm
- Excluded
- Opening tolerances, wire diameters, frame dimensions, sampling plans, inspection classes, calibration data, and test-method procedures
- Downloads
- Bulk CSV disabled; this page is intended as a lookup reference rather than a standards-data export
- Source check
- October 6, 2026
- 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.
A No. 40 sieve has a nominal opening of 425 µm, which is 0.425 mm or approximately 0.01673 in.
A No. 200 sieve has a nominal opening of 75 µm, equal to 0.075 mm or approximately 0.002953 in.
No. Microns are a length unit. A mesh or sieve number is a designation related to the wire-cloth pattern, so use the standardized designation-to-opening relationship rather than treating mesh as a direct length unit.
For the numbered U.S. sieve series, yes: higher numbers generally correspond to finer openings. For example, No. 40 is 425 µm while No. 200 is 75 µm.
Many nominal apertures align, but the standards are not interchangeable by label alone. Check the required standard, sieve series, tolerances, frame requirements, and test method for the job.
Find the Opening First, Then Verify the Test Requirement
Use the Sieve Size Chart to translate a U.S. sieve designation into millimeters, microns, or inches. For laboratory acceptance, procurement, or compliance, verify the current sieve standard, the governing material test method, and the actual sieve condition or certification required by the project.