USCS soil classification from Grain size and Atterberg limits

USCS Soil Classification Calculator

Classify soil using grain-size distribution and Atterberg limits. The calculator plots the grain-size distribution curve, evaluates gravel, sand, and fines fractions, computes D10, D30, D60, Cu, Cc, and assigns a USCS group symbol.

Input Data

Enter percent passing values from the grain-size analysis. Atterberg limits are required when fines influence classification.

Sieve Opening, mm Percent Passing, %
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Grain-Size Distribution Curve

Classification Result

USCS Group Symbol
–
Group Name
–
Soil Family
–
Plasticity Index
–

Soil Fractions

Gravel: –% Sand: –% Fines: –% Coarse: –%

Gradation Parameters

D10: – mm D30: – mm D60: – mm Cu: – Cc: –

Warnings / Notes

  • Run a classification to view notes.

Plasticity Chart

USCS Classification Basis and Formulas

Soil Fractions

P200 = percent passing No. 200 sieve
% Fines = P200
% Coarse = 100 – P200
% Gravel = 100 – P4
% Sand = P4 – P200

Gradation Parameters

Cu = D60 / D10
Cc = D30^2 / (D10 x D60)
Well-graded gravel: Cu >= 4 and 1 <= Cc <= 3
Well-graded sand: Cu >= 6 and 1 <= Cc <= 3

Plasticity Chart

PI = LL – PL
A-line: PI = 0.73(LL – 20)

Soils plotting above the A-line are generally clayey. Soils plotting below the A-line are generally silty.

References

ASTM D2487 – Standard Practice for Classification of Soils for Engineering Purposes.

ASTM D6913 / D6913M – Standard Test Methods for Particle-Size Distribution of Soils Using Sieve Analysis.

ASTM D7928 – Standard Test Method for Particle-Size Distribution of Fine-Grained Soils Using the Sedimentation Method.

ASTM D4318 – Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils.