What This Calculator Does
The Raised Garden Bed Soil Calculator tells you exactly how much soil to buy to fill one or more raised beds. Enter your bed dimensions and it returns the total volume in cubic feet, the equivalent in cubic yards, and how many bags of bagged soil or compost you'll need. This saves you from over-buying or making a second trip to the garden center.
How to Use It
Measure the inside length and width of your bed in feet and the soil depth you want in inches. Enter the number of identical beds you're filling, then pick your bag size (1.5 cubic feet is the most common). The calculator multiplies everything out and rounds the bag count up, because you can't buy a partial bag.
The Formula Explained
Volume is length × width × depth. Because depth is entered in inches, it is divided by 12 to convert to feet, so all three measurements share the same unit. Multiplying by the number of beds gives total cubic feet. To convert to cubic yards, divide by 27 (since 1 yard = 3 feet, and 3³ = 27). To get bags, divide total volume by the volume per bag and round up.
$$\text{Volume} = L \times W \times \frac{D}{12} \times N, \quad \text{Bags} = \frac{\text{Volume}}{\text{Bag Size}}$$
Worked Example
For a bed 8 ft long, 4 ft wide, filled 12 inches (1 ft) deep: $$8 \times 4 \times 1 = 32 \text{ cubic feet}.$$ That's \(32 \div 27 \approx 1.19\) cubic yards. Using 1.5 cu ft bags: \(32 \div 1.5 \approx 21.3\), so you'd buy 22 bags.
FAQ
How deep should soil be? Most vegetables thrive in 10–12 inches of soil; deep-rooted crops like carrots prefer more.
Should I buy a little extra? Yes — soil settles and compacts after watering, so adding 5–10% is wise.
Is it cheaper in bulk? Once you need more than about 1 cubic yard, bulk delivery is usually cheaper than bags.
