Casagrande Plasticity Chart
The Casagrande Plasticity Chart classifies fine-grained soils based on their Atterberg limits. Plot liquid limit (LL) against plasticity index (PI) to distinguish clays from silts and identify plasticity characteristics.
Enter data manually or paste directly from Excel.
⚠️ Results are indicative only — verify results independently.
Interpretation Guide
- CL:
- Inorganic Clay with low plasticity
- ML:
- Inorganic Silt with low plasticity
- OL:
- Organic Silt or Clay with low plasticity
- OH:
- Organic Silt or Clay with high plasticity
- MH:
- Inorganic Silt with high plasticity
- CH:
- Inorganic Clay with high plasticity
- A-Line:
- Line which separates the chart between clays and silts; soils plotting above the A-Line are classified as clays and those below are A-line are as silts
- U-Line:
- Line marking the approximate upper limit of naturally occurring soils
- LL=50:
- Vertical line at a Liquid Limit of 50'%' separates the high plasticity soils, 'LL>50', from the low plasticity soils 'LL<50'
Soil Types
Zones
References
- USCS – Unified Soil Classification System (ASTM D2487)
- Casagrande, A. Classification and identification of soils. Transactions, ASCE, vol.113, 901-930, 1948.
- Casagrande, A.: Notes on the Design of the Liquid Limit Device, Géotechnique, 8, 84-91, 1958.