Calculating cubic yards of soil is a fundamental process for anyone involved in landscaping, gardening, construction, or any project requiring the measurement of bulk materials like soil, mulch, gravel, or sand. A cubic yard is a unit of volume in the imperial and US customary systems. It represents the volume of a cube that is one yard on each side. Understanding how to calculate cubic yards of soil is crucial for accurate material purchasing, cost estimation, and ensuring you have the right amount of material without over- or under-ordering.
Who Should Use It:
Homeowners planning garden beds, lawn renovations, or patio installations; professional landscapers and contractors; construction site managers; farmers; and anyone needing to quantify a volume of material for a project.
Common Misconceptions:
A frequent mistake is confusing linear feet with cubic feet or yards. Soil is sold by volume, not by length or area alone. Another misconception is the depth measurement; it's often given in inches but needs conversion to feet for the cubic yard calculation. Also, many people underestimate the amount of soil needed, failing to account for settling or compaction, which can reduce the volume by 10-20%.
Cubic Yards of Soil Formula and Mathematical Explanation
The process of calculating cubic yards of soil involves converting all measurements to a consistent unit (feet) and then applying the formula for volume.
The standard formula for calculating the volume of a rectangular prism (like a soil bed or excavation area) is:
Volume = Length × Width × Depth
However, since soil is typically ordered in cubic yards, and measurements are often taken in feet for length and width, and inches for depth, we need to perform conversions.
Step-by-Step Derivation:
Convert Depth to Feet: Since 1 foot = 12 inches, divide the depth in inches by 12.
Depth (ft) = Depth (in) / 12
Calculate Volume in Cubic Feet: Multiply the length (ft), width (ft), and the converted depth (ft).
Volume (cu ft) = Length (ft) × Width (ft) × Depth (ft)
Convert Cubic Feet to Cubic Yards: There are 27 cubic feet in 1 cubic yard (3 ft × 3 ft × 3 ft = 27 cu ft). Divide the volume in cubic feet by 27.
Volume (cu yd) = Volume (cu ft) / 27
Combining these steps, the direct formula used in the calculator is:
Sarah wants to build a raised garden bed that is 12 feet long, 4 feet wide, and will be filled with 8 inches of new soil.
Length = 12 ft
Width = 4 ft
Depth = 8 in
Calculation:
Cubic Yards = (12 ft * 4 ft * 8 in) / 324
Cubic Yards = (384) / 324
Cubic Yards ≈ 1.185 cu yd
Interpretation: Sarah needs approximately 1.2 cubic yards of soil. It's wise to round up slightly to account for settling and ensure she has enough, perhaps ordering 1.25 or 1.5 cubic yards.
Example 2: Top Dressing a Lawn
A homeowner wants to add a 2-inch layer of topsoil to their backyard lawn, which measures 50 feet by 30 feet.
Length = 50 ft
Width = 30 ft
Depth = 2 in
Calculation:
Cubic Yards = (50 ft * 30 ft * 2 in) / 324
Cubic Yards = (3000) / 324
Cubic Yards ≈ 9.26 cu yd
Interpretation: The homeowner needs about 9.3 cubic yards of topsoil. For large lawn projects, it's common to order in bulk, and this calculation helps determine the quantity needed from a landscape supplier. They might round up to 9.5 or 10 cubic yards.
How to Use This Cubic Yards of Soil Calculator
Our calculator simplifies the process of determining how much soil you need. Follow these simple steps:
Measure Your Area: Use a tape measure to find the length and width of the space you need to fill with soil. Ensure these measurements are in feet.
Determine Desired Depth: Decide how deep you want the soil layer to be. Measure this depth in inches. Common depths include 4-6 inches for garden beds, 2-3 inches for lawn topdressing, or deeper for specific landscaping features.
Input Values: Enter the measured length (ft), width (ft), and depth (in) into the corresponding fields in the calculator.
Calculate: Click the "Calculate" button.
How to Read Results:
The calculator will display:
Primary Result (Cubic Yards): This is the total volume of soil needed, expressed in cubic yards. This is the number you'll typically use when ordering from suppliers.
Intermediate Values: You'll also see the total cubic feet, the depth converted to feet, and the total area in square feet. These can be helpful for understanding the scale of your project.
Decision-Making Guidance:
Always consider rounding up your final cubic yardage by 10-20%. Soil compacts significantly after being placed, watered, and settled. Ordering slightly more ensures you won't run short, which can be costly and inconvenient if you need to order a small additional amount later. For irregular shapes, break them down into simpler geometric forms (rectangles, triangles) and sum their volumes.
Key Factors That Affect Soil Volume Calculations
While the basic formula provides a solid estimate, several real-world factors can influence the actual amount of soil you need:
Compaction and Settling: This is the most significant factor. Freshly delivered soil is aerated and loose. Once placed, watered, and walked on, it will settle and compact, often reducing its volume by 10% to 20%. Always factor this in by ordering extra.
Irregular Shapes: The calculator assumes a perfect rectangular or square area. If your area is circular, triangular, or has an irregular shape, you'll need to adapt the calculation. For circles, use πr² for area. For irregular shapes, approximate them with simpler geometric shapes or use online area calculators.
Existing Ground Contours: If you're filling a sloped area, the depth might vary. You may need to calculate the average depth or calculate volumes for different sections with varying depths.
Material Type: Different soil types and amendments (like compost or mulch) have varying densities and compaction rates. While the volume calculation remains the same, how much they settle can differ.
Delivery Method and Bagged vs. Bulk: Bulk soil is usually sold by the cubic yard. Bagged soil often lists volume in cubic feet. Be sure to convert cubic feet to cubic yards (divide by 27) if comparing prices or quantities. Suppliers may also have minimum delivery quantities.
Waste and Spillage: During transport from the delivery point to the final location, or during the filling process, some soil may be spilled or lost. Account for a small buffer for this.
Project Specifics: For large construction projects, precise excavation and grading specifications are critical. For smaller garden projects, a bit of extra soil is usually more forgiving.
Frequently Asked Questions (FAQ)
Q1: How do I calculate cubic yards for a circular garden bed?
For a circle, first calculate the area in square feet using the formula: Area = π * radius². The radius is half the diameter. Then, convert the desired depth to feet (inches / 12). Finally, multiply the area (sq ft) by the depth (ft) to get cubic feet, and divide by 27 for cubic yards.
Q2: What's the difference between cubic feet and cubic yards?
A cubic yard is a larger unit of volume. One cubic yard is equal to 27 cubic feet (3 ft x 3 ft x 3 ft). Most bulk soil suppliers sell by the cubic yard, while bagged soil is often measured in cubic feet.
Q3: How much soil do I need for a 4×8 raised bed that's 10 inches deep?
Using the calculator or formula: (4 ft * 8 ft * 10 in) / 324 = 320 / 324 ≈ 0.99 cubic yards. It's best to round up to 1 to 1.25 cubic yards due to settling.
Q4: Should I account for settling when ordering soil?
Yes, absolutely. Soil compacts significantly after installation. It's standard practice to add an extra 10-20% to your calculated volume to ensure you have enough material.
Q5: My project area isn't a perfect rectangle. How do I calculate the soil needed?
Break down the irregular area into smaller, regular geometric shapes (rectangles, squares, triangles, circles). Calculate the volume for each section individually and then sum them up. Alternatively, estimate the total square footage of the area and use an average depth.
Q6: How deep should I make my garden beds?
For most vegetables and flowers, a depth of 6-12 inches is ideal. Shallow-rooted plants might be fine with 4-6 inches, while deep-rooted vegetables like carrots or potatoes benefit from 10-12 inches or more.
Q7: Can I use this calculator for mulch or gravel?
Yes, the principle is the same. This calculator determines volume. Whether it's soil, mulch, gravel, or sand, if you know the dimensions (length, width, depth) and need the volume in cubic yards, the calculation method is identical. Remember that different materials compact differently.
Q8: What if I need to calculate soil for an excavation?
Excavation calculations are similar but often involve removing soil rather than adding it. The volume calculation remains the same (Length x Width x Depth). However, excavation volumes might be measured differently depending on the project, and soil density can affect hauling capacity. Always consult project specifications for excavation.
Related Tools and Internal Resources
Soil Volume CalculatorUse our interactive tool to instantly calculate cubic yards of soil needed for your project.