A grain size distribution plot is a special purpose graph generally used to depict the results of a sieve analysis, commonly known as a "gradation test". The sieve analysis determines the gradation (the distribution of aggregate particles, by size, within a given sample) in order to determine compliance with design, production control requirements, and verification specifications.

Typically a grain size distribution plot shows grain sizes in millimeters on the X axis with a reversed (largest-to-smallest) logarithmic scale:

Grain Size Distribution Plot

DPlot shows material classifications below the X axis, using either the AASHTO (American Association of State Highway and Transportation Officials) designations or the Udden-Wentworth scale:
 

AASHTO material designation Udden-Wentworth scale
Size in
millimeters		Size classSize in
millimeters		Size class
500Cobbles 4096Boulder
76.2Coarse Gravel 256Cobble
19.05Fine Gravel 64Pebble
4.75Coarse Sand 4Granule
2.0Medium Sand 2.0Very Coarse Sand
0.425Fine Sand 1.0Coarse Sand
0.075Silt or Clay 0.5Medium Sand
 0.25Fine Sand
 0.125Very Fine Sand
 0.0625Coarse Silt
 0.031Medium Silt
 0.0156Fine Silt
 0.0078Very Fine Silt
 0.0039Clay

Sieve sizes are shown along the top of the graph using AASHTO-standard sizes as shown above, or British standard sieve sizes:

Grain Size Distribution Plot
 
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