Geotechnical and Hydraulics
Soil Particle Size Converter
Convert soil particle diameter between micrometers, millimeters, inches, and other length units.
Live unit conversion
Converted value
75
um
0.075 mm = 75 um
Conversion Basis
Particle-size data are reported in several units across sieve and hydrometer work. This converter changes diameter units only. Sieve designation is discrete and must be taken from the governing standard, not calculated from a continuous formula.
target diameter = source diameter x source-to-millimeter factor / target factor
Common Examples
- 0.075 mm = 75 um
- 4.75 mm = 0.187008 in
- 1 in = 25.4 mm
Engineering Use and Limitations
- Common classification boundaries depend on the selected system, such as USCS or AASHTO.
- A sieve number is a standard designation, not the reciprocal of opening size.
- Hydrometer-reported equivalent diameter depends on test assumptions in addition to unit conversion.
Common US standard sieve openings
These are nominal reference openings commonly used in US geotechnical practice. Confirm the governing ASTM or project standard for testing and reporting.
| Sieve | Nominal opening | Engineering note |
|---|---|---|
| No. 4 | 4.75 mm | Common gravel-sand boundary in USCS |
| No. 10 | 2.00 mm | Reference opening |
| No. 20 | 0.850 mm | Reference opening |
| No. 40 | 0.425 mm | Frequently used for Atterberg-limit preparation |
| No. 60 | 0.250 mm | Reference opening |
| No. 100 | 0.150 mm | Reference opening |
| No. 200 | 0.075 mm | Common coarse-fine boundary in USCS |
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