Atterberg limits & plasticity chart calculator

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Worked example — results

• ✓ Fit is good (R² ≥ 0.95) — R² = 0.998
• ✓ Point below U-line (physically plausible)

Method, formulas and assumptions

• LL = moisture at 20 mm cone penetration (linear fit)
• PI = LL − PL
• LI = (w − PL)/PI: LI < 0 hard, 0–1 plastic, > 1 liquid when remoulded
• A-line PI = 0.73(LL − 20); U-line PI = 0.9(LL − 8)
• Activity = PI / % clay (< 0.75 inactive, 0.75–1.25 normal, > 1.25 active)

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