How to calculate soil water content
Water content compares the mass of water with the mass of dry soil solids. The denominator is dry soil, not the total wet sample.
What the formula is saying
If wet and dry masses are given, first subtract dry from wet to obtain water mass. Divide water mass Mw by dry-solids mass Ms, then multiply by 100. This calculator reports the percentage.
Read the symbols in plain language
- Mw
- Mass of waterkg
- Ms
- Mass of dry solidskg
Sort out the units first
Use the same mass unit for numerator and denominator. A 1.2 kg wet sample and 1.0 kg dry solids contain 0.2 kg water, so enter Mw = 0.2 and Ms = 1.
Let’s solve one together
Read the given values, follow each operation, then check what the result means.
- Mw · Mass of water
- 0.2 kg
- Ms · Mass of dry solids
- 1 kg
Identify water mass only
Subtract container mass from measured masses before forming the soil quantities.
(0.2) = 0.2 kgDivide by dry-solids mass
The mass units cancel. This ratio is not yet a percent.
(0.2) ÷ (1) = 0.2Report as a percentage
Multiply the ratio by 100. A ratio of 0.20 is 20%; the calculator reports percent.
(0.2) × 100 = 20 %
Does this worked answer make sense?
The worked ratio 0.2 means 20%. Recombine the masses: 1.0 + 0.2 = 1.2 kg wet sample.
Now try your own values
Change a value or its unit. The same method will show your calculation, step by step.
Results update only when you calculate. The lesson example above stays unchanged.
Your turn — check your understanding
Use these new values. Work it out first, then check your answer.
- Mw · Mass of water
- 0.18 kg
- Ms · Mass of dry solids
- 0.6 kg
Find: soil water content
A hint, not the answer
If wet and dry masses are given, first subtract dry from wet to obtain water mass. Divide water mass Mw by dry-solids mass Ms, then multiply by 100. This calculator reports the percentage.
Use the same mass unit for numerator and denominator. A 1.2 kg wet sample and 1.0 kg dry solids contain 0.2 kg water, so enter Mw = 0.2 and Ms = 1.
Show the full practice solution
Compare the steps with your work; revealing a solution does not mark the lesson complete.
Identify water mass only
Subtract container mass from measured masses before forming the soil quantities.
(0.18) = 0.18 kgDivide by dry-solids mass
The mass units cancel. This ratio is not yet a percent.
(0.18) ÷ (0.6) = 0.3Report as a percentage
Multiply the ratio by 100. A ratio of 0.20 is 20%; the calculator reports percent.
(0.3) × 100 = 30 %
Avoid the common trap
Dividing by wet mass answers a different question. Do not multiply the displayed percentage by 100 again. A displayed 20% is a ratio of 0.20.
When this method applies — and when it does not
Gravimetric water-content definition using known water and dry-solids masses. This lesson does not prescribe laboratory drying procedures.
For study and understanding, not approval of a real structure, site operation or design. Apply the correct standard, National Annex and professional review to actual engineering work.
One idea understood. Keep going.
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Sources & further reading
References open in a new tab and explain the underlying principles. The teaching text and examples here are SimpleFlick’s own; the source organisations have not endorsed this calculator.
Lesson updated: · Worked examples checked against the implemented formula; not an independent engineering certification.