Dry Unit Weight of Soil Calculator

Calculator Inputs

The page uses one stacked layout. The form fields below switch to three columns on large screens, two on medium screens, and one on small screens.

Sample Label

Optional name for reports and exports.

Calculation Method

Choose the field data you already have.

Water Content (%)

Enter moisture content by dry mass percentage.

Moist Unit Weight

Moist Unit Weight Unit

Moist Density

Moist Density Unit

Wet Mass

Wet Mass Unit

Dry Mass

Dry Mass Unit

Total Volume

Total Volume Unit

Specific Gravity of Solids, Gs

Optional. Used for void ratio, porosity, and saturation.

Maximum Dry Unit Weight

Optional. Used for relative compaction.

Maximum Dry Unit Weight Unit

Example Data Table

Sample	Method	Input Summary	Calculated Dry Unit Weight	Dry Density
S-01	Moist unit weight + water content	γ = 18.60 kN/m³, w = 12.0%	16.61 kN/m³	1693.17 kg/m³
S-02	Wet mass + volume + water content	Wet mass = 1.84 kg, V = 0.00095 m³, w = 14.0%	16.67 kN/m³	1699.25 kg/m³
S-03	Dry mass + volume	Dry mass = 2.31 kg, V = 0.00125 m³	18.13 kN/m³	1848.00 kg/m³

Formula Used

1) From moist unit weight and water content
γ_d = γ / (1 + w)

2) From moist density and water content
ρ_d = ρ / (1 + w)

3) From dry mass and total volume
ρ_d = M_s / V and γ_d = ρ_d × g / 1000

4) State relationships when Gs is known
e = (G_s × γ_w / γ_d) − 1
n = e / (1 + e)
S_r = w × G_s / e

5) Relative compaction
RC = (γ_d,field / γ_d,max) × 100

Here, w is water content in decimal form, not percent. For example, 12% becomes 0.12. Keep mass, density, and volume units consistent before applying the formulas.

How to Use This Calculator

Select the calculation method that matches your field or lab data.
Enter moisture content if your method requires it.
Choose the correct units for mass, density, volume, or unit weight.
Optionally enter specific gravity to estimate void ratio, porosity, and saturation.
Optionally enter maximum dry unit weight to evaluate relative compaction.
Press the calculate button. The result appears above the form, directly below the header.
Use the chart and export buttons to document the result.

FAQs

1) What is dry unit weight of soil?

Dry unit weight is the soil weight per total volume after removing water mass from the calculation. It is widely used in compaction control, earthworks, pavement support checks, and geotechnical reporting.

2) Why is dry unit weight important in construction?

It helps engineers judge compaction quality and compare field conditions with design or laboratory targets. Better dry unit weight values usually indicate tighter particle packing and improved support behavior, though soil type still matters.

3) What is the difference between moist and dry unit weight?

Moist unit weight includes both soil solids and water. Dry unit weight removes the water contribution and represents only the solids over the same total volume. That makes it better for comparing compaction states.

4) When should I use γd = γ / (1 + w)?

Use it when you know the moist unit weight and the moisture content by dry mass. Convert moisture percentage into decimal form first. This is one of the most common field compaction calculations.

5) Can this calculator estimate relative compaction?

Yes. Enter the maximum dry unit weight from your laboratory compaction test. The calculator will compare your field dry unit weight against that maximum and report relative compaction as a percentage.

6) Why do I need specific gravity of solids?

Specific gravity lets the calculator estimate void ratio, porosity, and degree of saturation. These values are useful when you want more insight into soil structure, compaction condition, and moisture state.

7) Does the calculator work with field and lab data?

Yes. You can use moist unit weight, moist density, wet mass with volume, or dry mass with volume. That makes it useful for quick site checks and laboratory worksheet preparation.

8) Is this enough for final engineering approval?

No. It is a fast estimating and reporting tool. Final decisions should still consider soil classification, test method, sampling quality, specification limits, and project-specific engineering review.