Raised bed soil calculator
Enter your bed size and depth to get the volume of soil or growing mix to fill it, in cubic feet, cubic yards and bag counts.
Raised beds are usually filled 15–30 cm (6–12 in) deep.
- Compost (blend 3–5 sources): 8.9 cu ft
- Peat moss or coco coir: 8.9 cu ft
- Coarse vermiculite: 8.9 cu ft
How this is calculated
Volume = length × width × depth. Depth is converted from inches to feet (÷ 12), so cubic feet = length ft × width ft × (depth in ÷ 12). Cubic yards = cubic feet ÷ 27. Bag counts round up.
The even-thirds fill (roughly equal parts compost, a moisture-holding component such as peat or coir, and coarse vermiculite) is a widely used raised-bed recipe. Settle and top up after the first few waterings.
Common questions
What's the even-thirds mix and do I have to use it?
It's a widely-used raised-bed recipe: roughly equal parts compost, a moisture-holding material (peat moss or coir), and coarse vermiculite or perlite for drainage. It's a strong starting point, not a requirement - many gardeners substitute a bulk garden soil blend plus compost instead.
Why does the soil level drop after I fill the bed?
New soil settles as organic matter breaks down and air pockets compress, especially after the first few waterings. Budget for topping up 10-15% more within the first month.
Can I just use topsoil from my yard?
For a raised bed, straight topsoil is usually too dense and drains poorly once contained; blending it with compost and a coarse material gives roots the structure they need.