Raised bed soil calculator
A 4 × 8 ft bed filled 12 inches deep takes 32 cubic feet of soil: 1.19 cubic yards, or 22 bags of 1.5 cubic feet. Measure inside the walls, then change the example below.
For an L-shaped, U-shaped, hexagonal, octagonal or triangular bed, use the shaped-bed worksheet below the planner.
Example: a bed 8 × 4 ft inside, 12 in of soil
or mix your own: 15 topsoil+8 compost
- About 2,600 lb: 3 trips in a vehicle with 1,250 lb of room after its driver, or one delivered load.
- 1.2 cubic yards in bulk. Suppliers’ minimum loads run 1 to 5 yards, so get one delivered quote before buying 22 bags.
See how the bags are worked out
Answer: 22 bags of 1.5 ft³
- Measure inside the walls Inside, the bed is 8 ft long and 4 ft wide. Measure between the walls, not over them: the walls take up room the soil can’t.
- Find the soil depth The walls stand 14 in tall inside. Leave 2 in empty at the top and the soil is 12 in deep. Fill to that depth, not to the top of the walls.
- Work out the volume Length × width × depth: 96 × 48 × 12 in is 8 × 4 × 1 ft, so the soil fills 32 ft³.
- Divide by the bag size 32 ft³ ÷ 1.5 ft³ a bag = 21.33 bags. In the drawing each strip is one bag: 2.25 in wide, 12 in deep and 8 ft long.
- Round up to whole bags Bags come whole, so 21.33 becomes 22. Only 0.33 of the 22nd bag goes in; keep the rest for topping up.
12 in of soil: room for carrots and most crops. On open ground, roots carry on into the soil below the bed. Depth by crop
At other bag sizes: 43 of 0.75 ft³ · 32 of 1 ft³ · 22 of 1.5 ft³ · 16 of 2 ft³ · 11 of 3 ft³
Bed 1: 12 in of soil.
Weight uses Sands and Soils screened topsoil at 2,200 lb a cubic yard. Choose another material in Soil order.
Measure the inside of the bed
Choose a bed to start with
Soil depth is the inside height less the space you leave empty at the top for mulch and watering.
Prepare the spot for this bedLeave space to work around it
The outside size follows the inside plus 1.5-inch walls on each side, the thickness of a 2-inch board. Change it for a bed with thicker or thinner walls.
Sides refer to the drawing. For round containers, select all four sides to check reach from the whole rim. Layout clearances use the enclosing outside rectangle, including for round beds.
Work out your soil order
Split into your own mix
Already have a two-part soil mix in mind? Enter the percentage of each ingredient. Read the soil and surface guidance before choosing a mix.
Bag size for each ingredient
Compare your bag and bulk quotes
Private amounts stay on this page and are excluded from save, share and print. Enter 0 for a genuinely free delivery.
L-shaped, U-shaped, hexagonal and other bed shapes
Measure inside the walls. For an L or a U, enter the full outside length and width, then the part that is missing. For a hexagon or an octagon, enter one side. Several parts can be added together at the same fill depth. This worksheet is separate from the plan above and does not change it.
Soil for common bed sizes
The soil each size takes when filled 12 inches deep. Each page gives six depths, bag counts and the beds sold at that size.
2 ft wide
5 ft wide
6 ft wide
8 ft wide
For round pots from 12 to 36 inches, see soil for your bed or pot size.
Use the dimensions you actually plan to fill
All measurement fields in the garden planner change together between inches and centimeters. Leave the space above the soil empty. Extra soil starts at zero; add some only if you want more than the bed holds.
Round containers use a circular cross-section. The tapered-pot option uses the inside top and bottom diameters; a flexible bag may bulge, so a geometric estimate is approximate.
Bags at other sizes, and the weight
The plan above and the shaped-bed worksheet list the bag count at 0.75, 1, 1.5, 2 and 3 cubic feet, the sizes bagged soil is sold in (Scotts sells 0.75 cubic foot bags, Miracle-Gro 1, and Kellogg 1.5, 2 and 3). It also gives the weight, using one supplier’s screened topsoil at 2,200 lb a cubic yard, and the number of wheelbarrow loads and vehicle trips. A 4 × 8 ft bed filled 12 inches deep with that topsoil weighs about 2,600 lb.
Allow for settling
Fresh soil and compost sink after the first few waterings. Frame It All, a raised-bed maker, adds 10 percent to its own soil calculator for settling, and the “Add 10% for settling” button in the order step above uses that figure. The extra-soil box starts at zero so the bed’s own volume stays visible.
No extension service we cite publishes a percentage to add at the start. Washington State University Extension says to add soil every year or two to keep the full depth, and the University of Illinois Extension says a few inches of compost or topsoil a year should keep up. Utah State University Extension notes that moistening the mix before you fill reduces settling during the season.
How deep to fill
The University of Georgia Extension says most garden crops need at least 10 inches of soil. The wall height of a bed is not the fill depth; leave room at the top for mulch if you plan to use it.
A surface layer is a separate order. Use the mulch calculator for the top of the bed, or another calculator for the rest of the yard.