Soil Calculator

Data Source & Methodology

This calculator uses standard geometric formulas for volume and industry-standard values for material density and compaction. Data on soil densities are based on average geotechnical values referenced in landscaping architecture and civil engineering guides, such as data provided by university Cooperative Extension Services and landscaping suppliers.

All calculations are for estimation purposes. Actual material density can vary significantly based on moisture content and specific composition. We strongly recommend consulting your supplier for precise weight calculations.

The Formula Explained

The calculation is a multi-step process to find the final volume and weight.

1. Base Volume (Uncompacted)

First, we calculate the area of your space and multiply it by the depth to find the base volume.

\( V_{base} = Area \times Depth \)

The area depends on the shape you selected:

• Rectangular Area: \( Area = Length \times Width \)
• Circular Area: \( Area = \pi \times (\frac{Diameter}{2})^2 \) or \( \pi \times r^2 \)

2. Final Volume (With Compaction)

To account for soil settling, we multiply the base volume by a compaction factor. A factor of 1.2, for example, increases the required material by 20%.

\( V_{final} = V_{base} \times Compaction \, Factor \)

3. Estimated Weight

Finally, we multiply the final volume by the average density of the selected material to find the total estimated weight.

\( Weight = V_{final} \times Soil \, Density \)

Glossary of Variables

Base Volume

The initial volume of the space (Area × Depth) *before* accounting for compaction.

Required Volume

The final volume you should order, which includes the extra material needed for compaction.

Compaction Factor

A multiplier used to account for the fact that soil will "settle" or be packed down, occupying less space than when it was loose. A 1.2x factor means 20% compaction.

Soil Density

The weight of the material per unit of volume (e.g., tons per cubic yard). This varies significantly between sand, gravel, and topsoil.

How It Works: A Step-by-Step Example

Let's calculate the topsoil needed for a rectangular garden bed:

• Shape: Rectangle
• Length: 10 feet
• Width: 4 feet
• Depth: 6 inches
• Material: Topsoil (loose)

1. Unify Units: The depth is in inches, so we convert it to feet.
\( 6 \, inches \div 12 = 0.5 \, feet \)

2. Calculate Area:
\( Area = 10 \, ft \times 4 \, ft = 40 \, sq \, ft \)

3. Calculate Base Volume (cu ft):
\( V_{base} \, (ft^3) = 40 \, sq \, ft \times 0.5 \, ft = 20 \, cu \, ft \)

4. Convert to Cubic Yards: There are 27 cubic feet in 1 cubic yard.
\( V_{base} \, (yd^3) = 20 \, cu \, ft \div 27 = 0.74 \, cu \, yd \)

5. Apply Factors:
* Compaction: 'Loose' = 1.0 (no change)
* Density: Average Topsoil ≈ 1.2 tons / cu yd

6. Final Results:
* Required Volume: \( 0.74 \, cu \, yd \times 1.0 = 0.74 \, cu \, yd \)
* Estimated Weight: \( 0.74 \, cu \, yd \times 1.2 \, tons/cu \, yd = 0.89 \, tons \)

Frequently Asked Questions