Soil calculator for Illinois

For a 4 x 8 raised bed filled to 12 inches, the volume is 32 cubic feet of soil. That equals 1.2 cubic yards, often more than first-time builders expect from a few bags. Use this calculator for any bed, planter, or yard area and select from the three available soil types. Material weights differ: garden soil is about 2,000 lb per cubic yard, screened topsoil 2,200, and fill dirt 2,400. Selecting the intended material gives the correct ton estimate.

Three steps for bed math

1. Record every bed or planter measurement in feet. Use multiple-areas mode to combine the bed totals as you go.
2. Plan depth by use: improve established beds with 4-6 inches, allow 6 inches for new in-ground beds, and use 12 inches to fill raised planters from empty.
3. Find cubic yards by dividing cubic feet by 27. Convert yards to tons by multiplying by 1.0 to 1.2, based on soil type.

Coverage and weight

Choose soil by application

• For vegetable plots, flower borders, and planters, use garden soil blended with compost for planting.
• Choose screened topsoil for lawn areas and finish grading. The Topsoil Calculator includes lawn-depth guidance and examples.
• For filling holes or changing grade, place fill dirt below and reserve good soil for the planting layer.
• For worn native soil, work 2-3 inches of garden soil into the upper 6 inches instead of removing and replacing the full bed. This uses less material and helps roots establish sooner.

Fill raised beds with less blend

For deep beds, blended soil is not needed from bottom to top. A bed taller than 18 inches can use fill dirt, or coarse organic matter that composts in place, through the lower third, followed by 8-12 inches of garden soil where roots feed. Calculate each layer separately with two quick runs. In Illinois prairie clay, measure the full 12 inches rather than estimating the growing layer.

Example: three 4 x 8 beds

A bed area of Ninety-six square feet at 12 inches deep contains 96 cubic feet, equal to 3.6 cubic yards or about 3.6 tons of garden soil. Order 4 yards. As the compost portion settles roughly 10% in the first weeks, the remaining material can be used to bring beds back to level.

Amend clay and sand in place

Prairie clay is slow to drain, while sandy ground can lose moisture too quickly between waterings. Address either condition by tilling 2-3 inches of compost-blended garden soil through the upper 6 inches, then repeating over a couple of seasons. That requires a third of the material and lifting of full replacement. As roots and worms work downward, the blend continues improving the soil. Reserve complete replacement for beds where debris or contamination rules out the native ground.

Bulk soil or bagged soil

One cubic yard is about 36 bags at 40 lb each. A raised bed can require 43 bags, which means handling 43 bags twice. Bulk soil costs less per cubic foot and arrives as one tipped load, with free delivery. Save bags for topping off a single planter. Have the pile placed on a tarp: soil can stain concrete, and the tarp makes cleanup a simple drag-and-fold task.

Soil amounts for beds and bags

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