Raised Bed Soil Calculator
Enter your bed dimensions to get the exact soil volume, number of bags to buy, and a proven Mel's Mix recipe — in seconds.
Raised Bed Soil Calculator
Enter your bed size to see exactly how much soil you need.
Mel's Mix recipe (equal thirds)
- — cu ft compost / manure
- — cu ft peat moss or coco coir
- — cu ft coarse vermiculite
How much soil do I need for a raised bed?
Soil volume is simply length × width × depth. The trick most people miss: depth is in inches, so convert it to feet first (divide by 12). A 4×8 ft bed that is 12 inches deep needs 32 cubic feet; at 18 inches it jumps to 48. The calculator handles the math and converts it to bags for you.
Save money on deep beds
Plants only root in the top 8–12 inches, so you don't need premium mix all the way down. Use the hugelkultur / lasagna method for the bottom third and the calculator's hugelkultur toggle to see the savings. For the top layer, follow our best soil mix recipe.
Frequently asked questions
How much soil do I need for a 4x8 raised bed?
A 4×8 ft bed needs 32 cubic feet of soil at 12 inches deep, or 48 cubic feet at 18 inches deep. That is about 21 bags (1.5 cu ft) for the 12-inch bed.
How do you calculate soil for a raised bed?
Multiply length × width × depth in feet to get cubic feet. For a 4×8 ft bed that is 12 inches (1 ft) deep: 4 × 8 × 1 = 32 cubic feet. The calculator above does this for any size and converts it to bags.
How many bags of soil for a raised bed?
Divide the total cubic feet by the bag size. Most bagged soil is 1.5 cubic feet, so a 32 cubic-foot bed needs about 21 bags. Buy ~10% extra for settling.
Can I save money filling a deep bed?
Yes. Fill the bottom third with logs, branches, and leaves (the hugelkultur method) and only buy quality mix for the top 8–12 inches. Tick the hugelkultur box above to see the savings.