How to Calculate Soil
To determine how much soil you need for a garden bed or planter, measure its length, width, and desired depth.
Formula:
Volume (cubic feet) = Length (ft) × Width (ft) × Depth (ft)
Volume (cubic yards) = Volume (cubic feet) ÷ 27
Example Calculation
A raised garden bed is 8 ft long, 4 ft wide, and you want it filled to a depth of 12 inches (1 foot).
- Area: 8 × 4 = 32 sq ft
- Depth in feet: 12 / 12 = 1 ft
- Volume in cubic feet: 32 × 1 = 32 cubic ft
- Cubic yards: 32 / 27 = 1.18 cubic yards
You would need about 1.2 cubic yards of soil. If purchasing 1.5 cubic foot bags, you would divide 32 cubic feet by 1.5, requiring 22 bags.
How Much Should I Buy?
Soil naturally settles over time, especially after it is watered. It's recommended to add a 5% to 10% settling factor to your calculation to ensure your beds remain full after the first few rains.
Frequently Asked Questions
How much soil do I need?
Measure the length, width, and depth of your growing area. Use our soil calculator to instantly convert those dimensions into the number of bags or cubic yards you need to purchase.
How many bags of soil do I need?
This depends on the bag size. Typical garden soil bags are 1, 1.5, or 2 cubic feet. Divide your total required cubic feet by the volume of one bag. Our calculator lets you choose your bag size and does the math for you.
How many cubic yards are in a raised bed?
A standard 4x8 foot raised bed that is 1 foot deep holds exactly 32 cubic feet of soil, which is roughly 1.2 cubic yards.
Why does soil volume shrink over time?
Soil contains a lot of air when it is first dumped out of bags or delivered. As it gets wet and the organic matter breaks down, the soil compacts and settles.