Moisture Content Calculator
Gravimetric (water) content w is the mass of pore water divided by the mass of dry solids, expressed as a percentage: w = (M_water ÷ M_dry_solids) × 100.
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Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Weigh the empty tin, then weigh the moist soil plus tin before drying, and the same sample plus tin after oven-drying to constant mass at ~105–110 °C.
- Enter the wet mass, dry mass, and tin mass (all including the tin, in grams). The tin mass is subtracted automatically to isolate the dry solids.
- Read the moisture content w (%). Open the working panel to see the water mass and dry-solids mass used in the calculation.
How it works
Gravimetric (water) content w is the mass of pore water divided by the mass of dry solids, expressed as a percentage: w = (M_water ÷ M_dry_solids) × 100. The water mass is the difference between the wet and oven-dry masses, and the dry-solids mass is the oven-dry mass minus the tin, so any container weight cancels out.
Because the denominator is the DRY solid mass (not the total wet mass), w can legitimately exceed 100% for soft clays, peats, and organic soils that hold more water than solids. This is the standard geotechnical definition used in ASTM D2216 and AS 1289.2.1.1, and it feeds into void ratio, degree of saturation, and compaction (Proctor) calculations. Oven-drying to constant mass at 105–110 °C is assumed.
Worked example
Oven-dry moisture content of a soil sample. A tin weighs 32.10 g. A moist soil sample plus tin weighs 185.60 g; after oven-drying, the sample plus tin weighs 162.40 g. Mass of water = 185.60 − 162.40 = 23.20 g. Mass of dry solids = 162.40 − 32.10 = 130.30 g. Moisture content w = 23.20 ÷ 130.30 × 100 = 17.8%.
Common mistakes
- Dividing the water mass by the WET mass instead of the dry solids mass — that gives 'wet-basis' water content, a different (smaller) number than the geotechnical w.
- Forgetting to subtract the tin/container mass, which inflates the dry-solids figure and understates w.
- Not drying to constant mass (or drying gypseous/organic soils at too high a temperature), so residual or lost water biases the result.
Frequently asked questions
Why can moisture content be over 100%?
Because water content is measured against the DRY solid mass, not the total mass. If a soft clay or peat holds more water than solids, w exceeds 100% — that is normal and correct under the standard geotechnical definition.
Do I have to enter the masses including the tin?
Yes — enter the wet and dry masses as weighed with the tin, and enter the tin mass separately. The calculator subtracts the tin so both figures reduce to the soil solids only. If you already have net (tin-free) masses, just enter 0 for the tin.
Which standard does this follow?
The gravimetric water-content definition w = mass of water ÷ mass of dry solids × 100 as used in ASTM D2216 and AS 1289.2.1.1, assuming oven-drying to constant mass at about 105–110 °C. Results are guidance only; verify against the governing standard and a competent geotechnical professional.
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