Calculator Inputs
Use consistent force and volume units. Metric expects kN and m³. Imperial expects lb and ft³.
Example Data Table
| Total Weight | Volume | Moisture | Gs | Void Ratio | Moist Unit Weight | Dry Unit Weight | Saturated Unit Weight | Submerged Unit Weight |
|---|---|---|---|---|---|---|---|---|
| 18.6 kN | 1.2 m³ | 12% | 2.68 | 0.62 | 15.500 kN/m³ | 13.839 kN/m³ | 19.980 kN/m³ | 10.170 kN/m³ |
Formula Used
| Output | Formula | Meaning |
|---|---|---|
| Moist Unit Weight, γ | γ = W / V | Total soil weight divided by total sample volume. |
| Dry Unit Weight, γd | γd = γ / (1 + w) | w is moisture content written as a decimal. |
| Void Ratio, e | e = (Gs × γw / γd) - 1 | Derived when Gs and dry unit weight are known. |
| Saturated Unit Weight, γsat | γsat = ((Gs + e) / (1 + e)) × γw | Unit weight when soil voids are fully water filled. |
| Submerged Unit Weight, γ′ | γ′ = γsat - γw | Effective unit weight below the groundwater table. |
| Porosity, n | n = e / (1 + e) | Void volume expressed as a fraction of total volume. |
How to Use This Calculator
- Choose metric or imperial units first.
- Enter the total soil weight and sample volume.
- Add moisture content to calculate dry unit weight automatically.
- Enter specific gravity and void ratio for saturated results.
- Use the dry unit weight override when lab data exists.
- Click calculate to show the result block above the form.
- Review the chart, notes, and export options.
FAQs
1) What is soil unit weight?
Soil unit weight is the weight of soil per unit volume. It helps engineers estimate loads, settlement behavior, compaction targets, and earthwork quantities during design and field control.
2) Why are moist and dry unit weights different?
Moist unit weight includes the weight of solids and water. Dry unit weight removes water influence, so it is lower and better for comparing compaction conditions between samples.
3) When should I use saturated unit weight?
Use saturated unit weight when the soil voids are fully filled with water. This condition is common in below-water-table analysis, retaining structures, seepage zones, and submerged fills.
4) What does submerged unit weight represent?
Submerged unit weight is the effective weight of saturated soil underwater. It is the saturated unit weight minus water unit weight, and it is important for buoyancy-sensitive stability checks.
5) Can I calculate results without void ratio?
Yes. If you provide specific gravity and enough data to calculate dry unit weight, the calculator can derive void ratio automatically and then estimate saturated and submerged unit weights.
6) Which water unit weight should I enter?
Use 9.81 kN/m³ for standard metric work and 62.4 lb/ft³ for common imperial work, unless your project specification, fluid type, or temperature requires a different value.
7) Is this calculator suitable for compaction checks?
It is useful for quick screening and reporting, especially when comparing moist and dry conditions. Final acceptance should still follow project procedures, laboratory results, and field density testing standards.
8) What input consistency matters most?
Keep all units consistent. Weight and volume must match the chosen system, moisture content should be realistic, and specific gravity and void ratio should reflect the soil being analyzed.