Specific Gravity of Soil Calculator
Specific gravity of soil solids from a pycnometer test, using the dry-soil and water masses.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Gs = (W2 − W1) ÷ [(W4 − W1) − (W3 − W2)]
W1 = pycnometer, W2 = pycnometer + dry soil, W3 = pycnometer + soil + water, W4 = pycnometer + water only
Run the calculation to see each step with your own numbers.
Pycnometer 150 g; + 100 g dry soil = 250 g; + soil + water = 713 g; + water only = 650 g.
Dry soil mass = 250 − 150 = 100 g
Denominator = (650 − 150) − (713 − 250) = 500 − 463 = 37 g
Gs = 100 ÷ 37 = 2.703
- Water temperature during the test is close to the calibration temperature used for the pycnometer, or a temperature-correction factor has already been applied to W4 — this calculator does not apply one.
- The soil is fully de-aired (no trapped air bubbles) before the W3 reading, per ASTM D854 procedure — trapped air understates the soil volume and overstates Gs.
- Why does Gs matter?
- It converts between the mass and volume of the soil's solid particles — it's a required input for computing void ratio, porosity, degree of saturation and (with a moisture content) dry unit weight. Nearly every phase-relationship calculation in geotechnical engineering starts from Gs.
- What's a typical value?
- Most mineral (quartz/feldspar-dominated) soils run 2.65–2.75. Organic soils run lower (sometimes well under 2.5); soils rich in iron oxides or heavy minerals can run above 2.8.
- Does water temperature matter?
- Yes — water's density changes slightly with temperature, so ASTM D854 requires either running the test at a standard temperature or applying a correction factor to the water-mass readings. Apply any correction to your W4 value before entering it here.
Test method & formula
ASTM D854, 'Standard Test Methods for Specific Gravity of Soil Solids by Water Pycnometer'.
About the Specific Gravity of Soil Calculator
The Specific Gravity of Soil Calculator applies ASTM D854's pycnometer-method formula, turning four mass readings — the empty pycnometer, the pycnometer with dry soil, the pycnometer with soil and water together, and the pycnometer filled with water alone — into the specific gravity of the soil solids (Gs). Gs is a core input to phase-relationship calculations (void ratio, degree of saturation, dry unit weight) used throughout geotechnical design.
What you enter
- Pycnometer mass (W1)
- Pycnometer + dry soil mass (W2)
- Pycnometer + soil + water mass (W3)
- Pycnometer + water only mass (W4)
What you get back
- Specific gravity of soil solids (Gs) — Typical range for mineral soils: 2.60–2.80.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
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