Soil Classification Tool — USCS + AASHTO

Enter the sieve fractions (% passing the No.4 / No.10 / No.40 / No.200 sieves) and the Atterberg limits (LL, PL → PI). The app classifies your soil under the Unified Soil Classification System (ASTM D2487) and the AASHTO highway system (M 145), gives the group symbol, group name, and Group Index, shows the full worked reasoning, and plots your sample on the plasticity chart.

⛰️ Free to use · Balance … EP

① Which system?

USCS uses the No.4 & No.200 sieves; AASHTO uses No.10, No.40 & No.200. “Both” asks for all of them.

② Grain-size fractions (% passing)

% passing No.200 (0.075 mm — fines)

% passing No.4 (4.75 mm — USCS)

% passing No.10 (2.0 mm — AASHTO)

% passing No.40 (0.425 mm — AASHTO)

③ Gradation coefficients (clean coarse soils, fines < 12%)

D₁₀ (mm)

D₃₀ (mm)

D₆₀ (mm)

Cu = D₆₀/D₁₀ and Cc = D₃₀²/(D₁₀·D₆₀) are auto-computed.

Cu (uniformity)

Cc (curvature)

④ Atterberg limits

Nonplastic (NP) — no plasticity (sets PI = 0)

Liquid Limit LL

Plastic Limit PL (PI = LL − PL)

If you already know PI, you can type it in PL’s place by leaving LL and entering PI directly via the example, or enter LL & PL and PI is computed.

Organic soil (OL / OH · AASHTO A-8 peat note)

⛰️ Classification result

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Key parameters

Plasticity chart

A-line · PI = 0.73(LL−20) U-line · PI = 0.9(LL−8) Your sample

The point is only plotted when LL and PI are given (fine-grained or dirty coarse soils).

Worked reasoning

⚠️ Classification is a lab-data interpretation. Results depend on accurate grain-size and Atterberg testing. Borderline cases (dual symbols, points near the A-line / U-line) call for engineering judgment, and the group name follows D2487 conventions but a full visual-manual description (color, structure, gradation shape) is still required for a complete classification.