Oven-dry method (IS 2720 Part 2). Water content of soil from container and soil masses.
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Water Content of Soil Calculator: Free Online Tool
The soil water content calculator works out the moisture content of a soil sample from the oven-drying test. You enter the mass of the empty container, the mass of the container with wet soil and the mass of the container with oven-dried soil for up to three trials. The tool gives the water content of each trial as a percentage and the average.
Laboratory technicians, geotechnical engineers and students use the result in nearly every soil test, because water content affects strength, compaction and settlement. On site it is used to check whether borrow material or backfill is near the optimum moisture for compaction. The calculator follows the oven-dry method described in IS 2720 Part 2, so it saves time on repeated readings and avoids arithmetic mistakes in the laboratory sheet.
When to use this calculator
Use it after weighing samples from a field investigation, a compaction test, a Proctor test or a stockpile check. It is useful when you have three trial containers for the same soil and want the average quickly, or when you want to verify a hand calculation in a lab record. Leave unused trials blank, and the calculator will use only the trials that you filled in. It also gives a quick check on quotations and site requests before work starts. It also serves as a check on laboratory record sheets before they are signed and filed with the test report.
How to use the Water Content of Soil Calculator
- Open the calculator above on your phone, tablet or computer. Nothing needs to be installed and no sign-up is required.
- Enter your values in the input boxes: Empty container (g), Container + wet soil (g), Container + dry soil (g). The boxes already hold sample values, so overwrite them with your own.
- Press Calculate. The result appears straight away under the button.
- Change any value and press Calculate again to compare options. Press Reset to go back to the sample values.
- Check the result against your drawings, project specification and local code before you order material or approve work.
How the calculation works
For each trial, the mass of water is the mass of container with wet soil minus the mass of container with dry soil. The mass of dry soil is the container with dry soil minus the empty container. Water content w = (mass of water / mass of dry soil) x 100. The default first trial has 20.0 g, 55.0 g and 48.0 g, which gives 7.00 g of water, 28.00 g of dry soil and 25.00 percent. The average of the trials is shown at the end. Dry the soil in an oven at 105 to 110 degrees C until the mass is constant.
Worked example
When you open the page the calculator is filled with sample values. Pressing Calculate with those values gives the result below, which you can use to check that you are reading the output correctly.
| Water content of each trial | |
|---|---|
| Trial 1 (water 7.00 g, dry soil 28.00 g) | 25.00 % |
| Trial 2 (water 8.30 g, dry soil 30.40 g) | 27.30 % |
| Trial 3 (water 6.50 g, dry soil 26.10 g) | 24.90 % |
| Result | |
| Average water content | 25.74 % |
Tips and common mistakes
- Dry the sample at 105 to 110 degrees C until the mass stops changing, because an early reading will understate the water content.
- Weigh the empty container before every test and write the container number, since mixed-up numbers cause the most common record errors.
- Enter masses in grams, and use the same balance for all three readings in a trial to reduce small instrument differences.
- If the calculator reports an error, check that dry soil plus container is heavier than the empty container and not heavier than the wet reading.
- Compare trials with each other; a trial that differs strongly from the other two usually points to a weighing or sampling mistake.
Frequently asked questions
What formula does the calculator use?
Water content w equals the mass of water divided by the mass of dry soil, multiplied by 100. Mass of water is the wet reading minus the dry reading, and dry soil is the dry reading minus the empty container.
Why do I get a mass error?
The calculator checks that the dry reading is larger than the empty container and not larger than the wet reading. If this fails, a value was entered in the wrong box or a weighing was wrong, so recheck the three masses.
Can I enter fewer than three trials?
Yes. Leave a trial completely blank to skip it, and the average will be calculated from the trials you filled in. At least one complete trial is needed for a result.
At what temperature should the soil be dried?
The note says to dry the soil in an oven at 105 to 110 degrees C until the mass is constant. Weigh again after further drying to confirm that the mass no longer changes.
Can water content be more than 100 percent?
Yes, because it is based on the mass of dry soil, not the total mass. Very wet clays and organic soils can show values above 100 percent. The calculator does not limit the result.
Important note
This tool gives estimates for planning, study and quick checks. It does not replace design by a qualified engineer, site-specific testing, or the requirements of your project specification and local building code. Always confirm final quantities, test results and acceptance limits with the responsible engineer before using them for construction or payment.
