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Specific Gravity Calculator

Calculate specific gravity (Gs) of soil particles from pycnometer test masses per BS 1377-2. Enter M1-M4 to get Gs with typical value guidance.

Last updated 9 June 2026

About this tool

Calculate specific gravity (Gs) of soil particles from pycnometer test data per BS 1377-2. Enter the four standard masses from the gas jar or small pycnometer method and the tool calculates Gs automatically.

Gs is a fundamental soil property used in phase relationship calculations — void ratio, saturation, unit weight. It’s also needed for hydrometer analysis (sedimentation) calculations.

Standard: BS 1377-2:1990, Clause 8 (gas jar method) and Clause 8.3 (small pycnometer method).

How to use this tool

1. Enter mass of empty pycnometer (M1) — clean, dry container.

2. Enter mass of pycnometer + dry soil (M2) — oven-dried specimen.

3. Enter mass of pycnometer + soil + water (M3) — after de-airing.

4. Enter mass of pycnometer + water only (M4) — same temperature as M3.

Technical information

Gs = Ms / (Ms - (M3 - M4))

where Ms = M2 - M1 (mass of dry soil)

Typical values: Quartz sand 2.65 | Clay minerals 2.60–2.80 | Iron-rich soils 2.85–3.20 | Organic soils 1.50–2.00

Limitations

Accurate de-airing is critical. Incomplete removal of air bubbles from the soil–water mixture will give erroneously high Gs values.

Temperature must be consistent between M3 and M4 measurements. A 1°C difference can change Gs by ~0.01.

For soils containing soluble salts, Gs may be affected by dissolution during the test. Use kerosene as the displacement fluid for gypsiferous soils.

Revision history

9 June 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.

Spotted an error? Let us know.

Mass of pycnometer, M1 (g)

Empty pycnometer or gas jar

Mass of pycnometer + dry soil, M2 (g)

Must be greater than M1

Mass of pycnometer + soil + water, M3 (g)

After de-airing and topping up

Mass of pycnometer + water, M4 (g)

Pycnometer filled with water only

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