Garden Soil Calculator
Estimate the volume in cubic yards, cubic feet, and retail bag counts of premium garden soil needed for raised beds, planters, or garden beds.
Calculation Results
Total volume of garden soil needed in cubic feet, including waste/settling.
Total volume of garden soil needed in cubic yards, including waste/settling.
Estimated count of retail garden soil bags to purchase.
How This Calculator Works
To use the Garden Soil Calculator:
- Enter the length and width of the raised bed or garden zone.
- Specify the depth of soil needed (typically 6 to 12 inches for flowers and shallow veggies; 12 to 18 inches for root crops).
- Choose the retail bag size (1.5 cubic foot bags are the standard size in home centers).
- Add a waste/settling factor. 10% is standard because dry soil settles significantly after the first deep watering.
Formula & Calculations
Garden soil volume is calculated based on bed dimensions and fill depth, including a settling/waste buffer (typically 10% because loose soil compacts down after watering):
Volume (Cubic Feet) = Length × Width × Depth × (1 + Waste / 100)
To convert from cubic feet to cubic yards, we divide by 27:
Volume (Cubic Yards) = Volume (Cubic Feet) / 27
Premium soil is sold in bags ranging from 0.75 to 2.0 cubic feet. The bag requirement is calculated by dividing total cubic feet by bag size and rounding up to the nearest whole bag:
Bags Required = ceil(Volume in Cubic Feet / Bag Size)
Step-by-Step Calculation Examples
Raised Garden Bed
A 16ft x 4ft raised garden bed filled to a depth of 6 inches, using standard 1.5 cu ft soil bags and 10% settling waste.
- length: 16
- width: 4
- depth: 6
- bag_size: 1.5
- waste: 10
- volume_cu_ft: 35.2 cu ft
- volume_cu_yd: 1.30 cu yd
- bags_needed: 24
Frequently Asked Questions
How deep should soil be in a raised garden bed?
A minimum soil depth of 6 to 8 inches is required for most plants. For root vegetables (like carrots or potatoes) or large shrubs, a depth of 12 to 18 inches is highly recommended for proper root development.
How much does garden soil settle?
Loose bagged or bulk soil will settle by approximately 10% to 15% after it is first placed and watered. It is always wise to add a 10% settling allowance to avoid having under-filled beds.
What is the best soil mix for raised beds?
The ideal mix is 60% premium topsoil, 30% organic compost, and 10% peat moss or perlite. This creates a nutrient-rich, well-draining environment for plants.
How many bags of soil make up a cubic yard?
It takes exactly eighteen 1.5 cubic foot bags, or twenty-seven 1.0 cubic foot bags of soil to make one cubic yard (27 cubic feet).
Can I use potting soil in an outdoor garden bed?
Potting soil is designed for containers and is very light and sterile. It is too expensive and drains too quickly for large outdoor garden beds. Premium garden soil or raised bed soil is more appropriate.