Soil Moisture Content Calculator
Water content = (W2 − W3) ÷ (W3 − W1) × 100 — water driven off in the oven over the dry soil mass, per ASTM D2216 at 110 ± 5 °C. A 20 g container, 85 g wet and 72 g dried gives 13 g ÷ 52 g = 25.0%, by mass. Density: In-Situ Dry Density Calculator.
How it's calculated: Water content (%) = (W2 − W3) ÷ (W3 − W1) × 100, with W1 container, W2 container plus wet soil, W3 container plus oven-dry soil.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Water content (%) = (W2 − W3) ÷ (W3 − W1) × 100
W1 = container mass, W2 = container + wet soil, W3 = container + oven-dry soil
Run the calculation to see each step with your own numbers.
Container 20 g, container + wet soil 85 g, container + oven-dry soil 72 g.
Water = 85 − 72 = 13 g; dry soil = 72 − 20 = 52 g
Water content = 13 ÷ 52 × 100 = 25.0%
- Soil oven-dried to constant mass at 110 ± 5 °C per ASTM D2216 — a partially dried sample understates the water content.
- Water content here is gravimetric (mass of water ÷ mass of solids), the standard geotechnical convention — not volumetric water content.
- Why oven-dry at 110°C specifically?
- It's hot enough to drive off free and most absorbed pore water without decomposing organic matter or altering clay minerals in most soils — a lower temperature under-dries the sample, a much higher one can damage certain soils (e.g. gypsum-bearing or highly organic soils, which need a modified procedure).
- Is this the same as compaction moisture content?
- Yes — the same ASTM D2216 test and formula is used whether you're characterizing a natural sample, a Proctor compaction specimen, or a field density test's companion sample. This calculator's result plugs directly into the In-Situ Dry Density Calculator.
- What's a typical water content value?
- It varies enormously by soil type and site conditions — dry sand might read under 5%, while a saturated clay can read well over 40%. There's no universal 'normal' figure; compare it against the soil's plastic and liquid limits (Atterberg Limits Calculator) for context.
- How do you calculate soil moisture content?
- Subtract the oven-dry mass from the wet mass for the water, subtract the container for the dry soil, then divide water by dry soil and multiply by 100. 13 g of water in 52 g of dry soil is 25.0%.
- What masses do I need for a moisture content test?
- Three: the empty container (W1), the container with the wet soil (W2), and the container with the soil after oven-drying to constant mass (W3).
Test method & formula
ASTM D2216, 'Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass'.
About the Soil Moisture Content Calculator
The Soil Moisture Content Calculator applies ASTM D2216 — the standard oven-drying method — turning three scale readings (the container alone, the container with wet soil, and the container with oven-dried soil) into the soil's water content as a percentage of its dry mass. This is the single most common geotechnical lab measurement, and it feeds directly into the Atterberg Limits and In-Situ Dry Density calculators.
What you enter
- Container mass (W1)
- Container + wet soil mass (W2)
- Container + oven-dry soil mass (W3)
What you get back
- Water content — %
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Specific Gravity of Soil Calculator — Specific gravity of soil solids from a pycnometer test, using the dry-soil and water masses.
- Atterberg Limits Calculator — Liquid limit (one-point method), plastic limit and plasticity index of a fine-grained soil.
- In-Situ Dry Density Calculator — Field bulk density, dry density and percent compaction of compacted soil from a drive-cylinder (core cutter) sample.
- California Bearing Ratio (CBR) Calculator — California Bearing Ratio of a subgrade or base sample at 2.5 mm and 5.0 mm penetration, against the ASTM standard loads.
Related articles
- What Is Soil Moisture Content? — Soil moisture content is the weight of water in a sample relative to its dry weight — and it's one of the most consequential numbers in earthwork.
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