Inputs
Provide wet and dry masses. Add volume and porosity for expanded outputs.
Formula used
-
Gravimetric moisture content:
w = (mwet − mdry) / mdry, andw% = 100 × w. -
Bulk density (if not entered):
ρb = mdry / V. -
Volumetric water content (using ρw ≈ 1 g/cm³):
θv = w × ρb / ρw, andθv% = 100 × θv. -
Degree of saturation (requires porosity n):
S% = 100 × θv / n.
How to use this calculator
- Collect a representative soil sample and weigh it wet.
- Oven-dry the sample (per your procedure), then weigh dry.
- Enter wet and dry masses, and choose the mass unit.
- Optional: enter sample volume or bulk density for volumetric output.
- Optional: enter porosity to estimate degree of saturation.
- Press Calculate, then download CSV or PDF for records.
Example data table
| Wet mass (g) | Dry mass (g) | Volume (cm³) | Porosity (%) | Moisture (%) | Volumetric (% v/v) | Saturation (%) |
|---|---|---|---|---|---|---|
| 520 | 470 | 300 | 38 | 10.64 | 16.67 | 43.86 |
| 610 | 540 | 320 | 35 | 12.96 | 21.88 | 62.50 |
| 780 | 650 | 360 | 40 | 20.00 | 36.11 | 90.28 |
These examples assume bulk density is computed from dry mass ÷ volume.
Why soil moisture matters for construction
Moisture content controls how soil behaves during excavation, hauling, placement, and compaction. When water is too low, particles resist rearrangement and fines can dust. When water is high, pore water reduces effective stress, increasing rutting and pumping risk. Tracking moisture supports stable lifts and predictable performance.
Key moisture metrics used on site
Gravimetric moisture is the mass of water relative to dry soil mass, reported as a percent. Volumetric moisture expresses water volume per total sample volume, often used when comparing different densities. Degree of saturation compares volumetric moisture to porosity, indicating how full the voids are.
Reliable sampling and drying workflow
Collect representative material from the lift, avoiding surface crust and obvious pockets. Seal samples quickly to prevent evaporation. Determine wet mass, then dry using your approved method and measure dry mass. Record sample ID, location, depth, and time. Consistent handling reduces variability between tests.
Interpreting typical moisture ranges
Many granular fills perform well at relatively low moisture, while fine-grained soils often need higher moisture to compact effectively. In the example table, gravimetric moisture spans about 10.6% to 20.0%, with saturation rising toward 90%. Values near saturation commonly signal reduced shear strength and slower drying.
Connecting moisture to compaction control
Moisture and density work together. Compaction effort is most efficient near the moisture range that yields maximum dry density in your project testing program. If field moisture is low, add water and mix thoroughly. If high, aerate, scarify, or blend with drier material before rolling.
Using bulk density and porosity options
This tool estimates volumetric moisture using bulk density, either entered directly or computed from dry mass and sample volume. When porosity is provided, the calculator reports degree of saturation. These optional outputs help compare soils across varying densities and support drainage assessments for trenches, subgrades, and backfills.
Documentation and quality assurance benefits
Moisture records improve traceability for earthworks acceptance and corrective actions. Exported CSV files support daily reports, while PDF summaries are useful for inspection packets. Store test dates, locations, lift thickness, and weather notes alongside results. Clear documentation reduces disputes and accelerates approvals.
Practical limitations and good practice
Moisture results depend on sample integrity, drying completeness, and unit accuracy. Avoid using a single test to represent large areas; instead, test at meaningful intervals and after material changes. Use this calculator as a decision aid alongside project specifications and field observations.
FAQs
1) What is the difference between gravimetric and volumetric moisture?
Gravimetric moisture compares water mass to dry soil mass. Volumetric moisture estimates water volume per total sample volume and depends on bulk density. Both describe water content, but they scale differently across densities.
2) Do I need sample volume to use this calculator?
No. Wet and dry masses are enough to compute gravimetric moisture. Sample volume is only needed if you want the calculator to estimate bulk density and provide volumetric moisture and saturation outputs.
3) When should I enter bulk density instead of volume?
Enter bulk density when you already have a field or lab measurement. This can be faster and may be more representative than calculating density from a small volume sample, especially for coarse or layered materials.
4) What porosity value should I use?
Use porosity from project testing, published references for your material type, or a value derived from bulk and particle densities. Porosity should be between 0 and 1 (or 0–100%).
5) Why does the tool show saturation above 100%?
Saturation above 100% usually indicates inconsistent inputs, such as an underestimated porosity or an overestimated bulk density. Recheck units, volume, and porosity assumptions, then rerun the calculation.
6) How can I use moisture results to decide next actions?
Compare measured moisture to your target range from compaction testing. If low, add water and mix; if high, aerate, blend, or improve drainage. Confirm with additional tests after adjustments.
7) Are the CSV and PDF downloads site-safe for recordkeeping?
Yes. The downloads reflect the latest computed values stored in your session and are suitable for attaching to daily logs. For audits, also record sample identifiers, locations, and any field observations.
Accurate moisture checks help safer, stronger, longer-lasting construction outcomes.