Figuring out how much dirt you need for your project is a common task for homeowners and landscapers alike. To calculate a yard of dirt, you’ll need to know the dimensions of the area you’re filling and then convert those measurements into cubic yards.
Calculating Your Dirt Needs: A Step-by-Step Guide
Planning a landscaping project often involves ordering materials like soil, mulch, or gravel. Getting the quantity right is crucial to avoid costly over-ordering or inconvenient under-ordering. This guide will walk you through the process of figuring out how much dirt you need, ensuring you have exactly what you require for your garden beds, lawn repairs, or other landscaping endeavors.
Why Accurate Dirt Estimation Matters
When undertaking any project that involves filling or covering an area with dirt, knowing the precise amount you need is essential. This isn’t just about convenience; it directly impacts your budget and the success of your project.
- Cost Savings: Buying dirt in bulk is usually more economical than purchasing small bags. However, you still need to buy the correct amount. Overestimating means you’ve paid for soil you won’t use, and underestimating means you’ll have to make another trip and potentially pay for delivery again.
- Project Efficiency: Running out of soil midway through filling a garden bed or grading a lawn is a major setback. It disrupts your workflow, delays your project, and can lead to uneven results if you try to make do with less.
- Environmental Impact: While dirt is a natural resource, responsible purchasing minimizes waste. Ordering only what you need helps reduce unnecessary transportation and production.
Comprehending “A Yard of Dirt”
The term “yard of dirt” or “cubic yard” is a unit of volume. It represents a cube that is 3 feet long, 3 feet wide, and 3 feet high.
1 Cubic Yard = 3 feet x 3 feet x 3 feet = 27 cubic feet
When you buy dirt in bulk, it’s typically sold by the cubic yard. This is why your primary goal will be to convert your project’s dimensions into cubic yards.
Measuring Your Project Area
Before you can calculate cubic yards of soil, you need to measure the space you intend to fill. The most common shapes you’ll encounter are rectangles and squares, but you might also deal with circular or irregularly shaped areas.
Measuring Rectangular or Square Areas
For simple rectangular or square areas, you’ll need two measurements: length and width.
- Length: Measure the longest side of your area.
- Width: Measure the shorter side of your area.
Ensure you measure in consistent units, preferably feet, as this is what we’ll use for the cubic yard calculation.
Example: You want to fill a raised garden bed that is 8 feet long and 4 feet wide.
Measuring Circular Areas
For circular areas, you’ll need to measure the diameter or the radius.
- Diameter: Measure the distance across the center of the circle, from one edge to the other.
- Radius: Measure from the center of the circle to its edge. The radius is half the diameter.
Example: You have a circular flower bed with a diameter of 6 feet.
Measuring Irregularly Shaped Areas
For areas that aren’t simple shapes, you can break them down into smaller, manageable geometric shapes (rectangles, squares, triangles, circles). Calculate the area of each smaller shape and then add them together.
Calculating the Area of Your Space
Once you have your measurements, you can calculate the surface area of your project.
-
Rectangles and Squares:
Area = Length x Width- Using our garden bed example:
Area = 8 feet x 4 feet = 32 square feet
- Using our garden bed example:
-
Circles:
Area = π x (radius)² (where π is approximately 3.14)- Using our circular flower bed example:
First, find the radius: Radius = Diameter / 2 = 6 feet / 2 = 3 feet
Area = 3.14 x (3 feet)² = 3.14 x 9 square feet = 28.26 square feet
- Using our circular flower bed example:
Determining the Depth Needed
This is where many people stumble. You’re not just covering an area; you’re filling it to a certain depth. This depth is the third dimension needed to calculate volume.
Think about how deep you want the soil to be.
- For a garden bed: You might want 6 inches or 12 inches of new soil.
- For a lawn patch: You might need 4 inches to level it out.
- For a base layer: You might need a specific depth for a driveway or patio project.
Crucially, convert your depth measurement to feet.
- 1 inch = 1/12 feet (or approximately 0.083 feet)
- 6 inches = 6/12 feet = 0.5 feet
- 12 inches = 12/12 feet = 1 foot
- 4 inches = 4/12 feet = 0.33 feet
Example Depth Measurements:
- If you need 6 inches of soil, that’s 0.5 feet.
- If you need 4 inches of soil, that’s 0.33 feet.
Calculating the Volume (in Cubic Feet)
Now you have the surface area (in square feet) and the depth (in feet). To find the volume, you multiply these two numbers.
Volume (cubic feet) = Area (square feet) x Depth (feet)
Let’s continue with our examples:
-
Garden Bed:
Surface Area = 32 square feet
Desired Depth = 6 inches = 0.5 feet
Volume = 32 square feet x 0.5 feet = 16 cubic feet -
Circular Flower Bed:
Surface Area = 28.26 square feet
Desired Depth = 4 inches = 0.33 feet
Volume = 28.26 square feet x 0.33 feet = 9.33 cubic feet
Converting Cubic Feet to Cubic Yards
The final step is to convert your calculated volume from cubic feet to cubic yards. Remember, 1 cubic yard equals 27 cubic feet.
Volume (cubic yards) = Volume (cubic feet) / 27
Continuing with our examples:
-
Garden Bed:
Volume (cubic feet) = 16 cubic feet
Volume (cubic yards) = 16 cubic feet / 27 cubic feet/cubic yard ≈ 0.59 cubic yards -
Circular Flower Bed:
Volume (cubic feet) = 9.33 cubic feet
Volume (cubic yards) = 9.33 cubic feet / 27 cubic feet/cubic yard ≈ 0.35 cubic yards
This calculation tells you exactly how much soil you need for those specific dimensions.
Practical Tips for Estimating Landscaping Materials
When you’re estimating landscaping materials like soil, a little extra foresight can save you time and hassle.
- Round Up: It’s almost always better to have a little extra than to run short. If your calculation results in a fraction of a yard (like 0.59 cubic yards), consider rounding up to the nearest half or whole yard. For the garden bed example, ordering 0.75 or 1 cubic yard would be wise. For the circular bed, ordering 0.5 cubic yards might suffice if it’s a small area, but 1 cubic yard gives you a buffer.
- Consider Compaction: Some soils, especially loams and organic matter-rich soils, will compact slightly after being placed and watered. If you’re ordering a very specific depth, you might want to factor in a small percentage for compaction. However, for most typical landscaping needs, calculating to the desired final depth is usually sufficient.
- Bagged vs. Bulk: If your project is small and requires less than half a cubic yard, buying bagged soil might be more practical. A standard bag of topsoil (often around 1.5 to 2 cubic feet) can be converted to yards by dividing its volume by 27. For example, if a bag is 2 cubic feet, you’d need 27 / 2 = 13.5 bags to make one cubic yard. If you need 0.5 cubic yards, that’s 13.5 / 2 = 6.75 bags, so 7 bags.
- Delivery Minimums: Bulk suppliers often have minimum order quantities for delivery. If your calculated amount is below their minimum, you might need to increase your order slightly to qualify for delivery, or arrange for pickup.
- Soil Density: While not usually a concern for cubic yard calculations, be aware that different types of soil have different densities. This matters more if you’re ordering by weight, but since dirt is sold by volume (cubic yards), density is less of a factor for this calculation.
Using a Dirt Calculator
Many online retailers and landscaping supply companies offer free dirt calculator tools. These can be incredibly helpful, especially if you’re not comfortable with the calculations or have complex shapes. You typically input your measurements (length, width, depth), and the calculator does the rest, often providing the answer directly in cubic yards. This is a fantastic way to double-check your own calculations or to quickly estimate how much soil do I need.
Common Project Examples and Calculations
Let’s work through a few more scenarios to solidify your grasping of soil calculation for gardens and other projects.
Scenario 1: Filling a Rectangular Lawn Area
- Problem: You need to add 4 inches of topsoil to a rectangular lawn area that is 20 feet long and 15 feet wide.
- Step 1: Measure: Length = 20 ft, Width = 15 ft.
- Step 2: Calculate Area: Area = 20 ft x 15 ft = 300 sq ft.
- Step 3: Determine Depth: Depth = 4 inches = 4/12 ft = 0.33 ft.
- Step 4: Calculate Volume (cubic feet): Volume = 300 sq ft x 0.33 ft = 99 cubic feet.
- Step 5: Convert to Cubic Yards: Volume = 99 cubic feet / 27 cubic feet/cubic yard ≈ 3.67 cubic yards.
- Recommendation: Order 4 cubic yards to be safe.
Scenario 2: Creating a New Garden Bed
- Problem: You’re building a new raised garden bed with dimensions 10 feet long, 5 feet wide, and you want the soil level to be 1 foot deep.
- Step 1: Measure: Length = 10 ft, Width = 5 ft.
- Step 2: Calculate Area: Area = 10 ft x 5 ft = 50 sq ft.
- Step 3: Determine Depth: Depth = 1 ft.
- Step 4: Calculate Volume (cubic feet): Volume = 50 sq ft x 1 ft = 50 cubic feet.
- Step 5: Convert to Cubic Yards: Volume = 50 cubic feet / 27 cubic feet/cubic yard ≈ 1.85 cubic yards.
- Recommendation: Order 2 cubic yards.
Scenario 3: Covering a Circular Patio Base
- Problem: You need to fill a circular area with 6 inches of gravel for a patio base. The diameter of the area is 12 feet.
- Step 1: Measure: Diameter = 12 ft.
- Step 2: Calculate Radius: Radius = 12 ft / 2 = 6 ft.
- Step 3: Calculate Area: Area = π x (6 ft)² = 3.14 x 36 sq ft = 113.04 sq ft.
- Step 4: Determine Depth: Depth = 6 inches = 0.5 ft.
- Step 5: Calculate Volume (cubic feet): Volume = 113.04 sq ft x 0.5 ft = 56.52 cubic feet.
- Step 6: Convert to Cubic Yards: Volume = 56.52 cubic feet / 27 cubic feet/cubic yard ≈ 2.1 cubic yards.
- Recommendation: Order 2.25 or 2.5 cubic yards of gravel.
Tables for Quick Reference
To help visualize the conversion, here are a few common depths and their equivalent in feet, and a general guide for converting cubic feet to cubic yards.
Table 1: Common Depths and Their Feet Equivalents
| Depth in Inches | Depth in Feet |
|---|---|
| 1 | 0.083 |
| 2 | 0.167 |
| 3 | 0.25 |
| 4 | 0.333 |
| 5 | 0.417 |
| 6 | 0.5 |
| 8 | 0.667 |
| 10 | 0.833 |
| 12 | 1 |
Table 2: Cubic Feet to Cubic Yards Conversion
| Cubic Feet | Cubic Yards |
|---|---|
| 27 | 1 |
| 54 | 2 |
| 81 | 3 |
| 108 | 4 |
| 135 | 5 |
Table 3: Estimating Soil Needs for Garden Beds (Common Sizes)
This table provides estimated cubic yards needed for common garden bed dimensions at a depth of 6 inches (0.5 ft).
| Garden Bed Length (ft) | Garden Bed Width (ft) | Area (sq ft) | Volume (cu ft) | Volume (cu yd) | Order (cu yd) |
|---|---|---|---|---|---|
| 4 | 4 | 16 | 8 | 0.3 | 0.5 |
| 6 | 4 | 24 | 12 | 0.4 | 0.5 |
| 8 | 4 | 32 | 16 | 0.6 | 0.75 |
| 8 | 6 | 48 | 24 | 0.9 | 1 |
| 10 | 5 | 50 | 25 | 0.9 | 1 |
| 10 | 8 | 80 | 40 | 1.5 | 1.5 |
| 12 | 8 | 96 | 48 | 1.8 | 2 |
Fathoming the Process of Buying Dirt in Bulk
When you’re ready to buy, you’ll likely be purchasing from a landscape supply yard or a garden center that sells soil by the cubic yard. Here’s what to expect:
- The Calculation: Use the methods described above to determine your cubic yard needs.
- Contacting Suppliers: Call your local suppliers. Ask about their soil types (topsoil, compost, blended mixes), pricing per cubic yard, delivery fees, and any minimum order quantities.
- Delivery vs. Pickup: Decide if you want the dirt delivered or if you’ll pick it up yourself. If picking up, ensure your vehicle is capable of hauling the weight and volume. A cubic yard of soil can weigh between 1,000 to 1,500 pounds or more, depending on moisture content and composition.
- Placing the Order: Clearly state the type and the exact number of cubic yards you need. It’s a good idea to confirm your calculation with the supplier’s representative, as they can often help you refine your estimate based on common project needs.
- Scheduling Delivery: If you opt for delivery, schedule it in advance to ensure it arrives when you need it. Make sure you have a clear, accessible location for the delivery truck to dump the soil.
Frequently Asked Questions (FAQ)
Q: What is the difference between a square foot and a cubic yard?
A: A square foot is a unit of area (length x width), while a cubic yard is a unit of volume (length x width x depth). You need to calculate both to figure out how much dirt you need.
Q: Can I just measure the area and guess the depth?
A: While you can guess, it’s much more accurate to measure the desired depth of your soil. This ensures you get the correct volume and avoid under or over-ordering.
Q: How do I measure soil for a sloped area?
A: For sloped areas, it’s best to take measurements at several points and find an average depth. For example, measure the depth at the lowest point and the highest point, add them, and divide by two to get an average depth. Then use this average depth in your volume calculation.
Q: What if I need different types of soil, like compost and topsoil?
A: Calculate the amount needed for each type separately. For example, if you need 4 cubic yards of soil and want to mix 75% topsoil with 25% compost, you’d calculate 3 cubic yards of topsoil (4 x 0.75) and 1 cubic yard of compost (4 x 0.25).
Q: How much does a cubic yard of dirt weigh?
A: The weight can vary significantly based on the type of soil and its moisture content. A general estimate for a cubic yard of topsoil is between 1,000 to 1,500 pounds. Always confirm with your supplier if weight is a concern for transport.
Q: What is a landscaping dirt estimate?
A: A landscaping dirt estimate is the process of calculating the total volume of soil or other landscaping materials needed for a specific project, usually expressed in cubic yards.
By following these steps, you can confidently calculate your dirt needs for any project, ensuring you have the right amount of material to achieve beautiful and functional results.