Raised Bed Soil Calculator
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Your Soil Requirements
Total Volume (Cubic Feet):
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Total Volume (Cubic Yards):
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Total Bags Needed:
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Estimated Total Cost:
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*Calculations include a 10% buffer for soil settling.
How to Use the Raised Bed Soil Calculator
Building a garden is an investment in your home and health. The most common mistake new gardeners make is underestimating how much soil is required to fill a new raised bed. This calculator helps you determine the exact volume of soil needed in cubic feet, cubic yards, and standard retail bags.
The 10% Settling Rule: This calculator automatically adds 10% to your final total. Why? Because garden soil contains air pockets that collapse after the first few waterings, causing the soil level to drop.
The Math Behind Raised Bed Volume
To calculate the volume of a rectangular raised bed, we use the following formula:
- Step 1: Multiply Length (ft) × Width (ft) to get the area.
- Step 2: Convert Depth (inches) to feet by dividing by 12.
- Step 3: Multiply the Area by the Depth (ft) to get Cubic Feet.
- Step 4: To get Cubic Yards, divide the total Cubic Feet by 27.
What is the Best Soil Mix for Raised Beds?
You shouldn't just fill a raised bed with native "dirt" from your yard. It's often too heavy and lacks the drainage necessary for containerized growing. Most experts recommend a blend:
- 60% Topsoil: The base of your bed.
- 30% Compost: Provides essential nutrients and organic matter.
- 10% Potting Mix or Peat Moss/Perlite: Ensures aeration and moisture retention.
Bulk Soil vs. Bagged Soil
Determining whether to buy in bulk or by the bag depends on your total volume. Generally, if you need more than 1 cubic yard (27 cubic feet), buying in bulk from a local landscape supply company is significantly cheaper. For smaller beds or herb gardens, 2.0 cubic foot bags from a garden center are more convenient for transport.
Example Calculation
If you have two 4×8 beds that are 12 inches deep:
- Volume per bed: 4′ × 8′ × 1′ = 32 Cubic Feet.
- Total for two beds: 64 Cubic Feet.
- Adding 10% for settling: ~70.4 Cubic Feet.
- In Cubic Yards: 70.4 / 27 = 2.6 Cubic Yards.