Calculate the degree of saturation from water content, specific gravity, and void ratio.
Degree of saturation (S) indicates what percentage of the void space is filled with water, ranging from 0% (completely dry) to 100% (fully saturated). It is a key parameter for understanding soil behaviour — effective stress, shear strength, and compressibility all depend on whether the soil is saturated or partially saturated.
Useful for cross-checking lab data, verifying whether samples are fully saturated, and supporting geotechnical classification.
Enter water content (w) — as a percentage, from lab moisture content tests.Enter specific gravity (Gs) — defaults to 2.65. Adjust for clay minerals or test-specific values.Enter void ratio (e) — from laboratory testing or calculated using the Void Ratio Calculator.Review the result — shown as a percentage and decimal, with an approximate description of the saturation state.The tool uses the standard phase relationship:
S = w × Gs / e where S = degree of saturation, w = water content (decimal), Gs = specific gravity, e = void ratio.
This is a rearrangement of the canonical form Se = wGs, found in all standard geotechnical references including Craig's Soil Mechanics and Das's Principles of Geotechnical Engineering.
Saturation is capped at 100% as it cannot physically exceed this value. Soils below the water table are typically fully saturated; above it, saturation varies with capillary effects and soil type.
The descriptive labels (e.g. "Highly saturated", "Moist") are approximate guidance categories, not formal geotechnical classifications.
Limitations A computed saturation above 100% indicates inconsistent input data — check that Gs, w, and e are from the same sample and test series. Field estimation of saturation is inherently less reliable than laboratory determination. Where possible, use lab-derived inputs. For partially saturated soils, matric suction and unsaturated soil mechanics may be more appropriate than simple phase relationships. Revision history 1 April 2026: Initial release.
Disclaimer This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.
Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.
All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.
By using this tool, you accept full responsibility for how you interpret and apply the information provided.
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