Raised Bed Soil Calculator

Calculate soil bags using inside dimensions and remaining fill depth.

1. Enter dimensions

Example — edit to match your project.

Garden bed illustration with plants and a visible layer of growing material — 32 sq ft · illustration, not to scale

THE MATH, MADE CLEAR

How much soil does a raised bed need?

Cubic feet = inside length (ft) × inside width (ft) × remaining fill depth (in) ÷ 12.

For several beds, calculate each volume and add the volumes before rounding bags. For identical beds, multiply one bed’s volume by the number of beds.

Cubic yards = total cubic feet ÷ 27. In metric units, cubic meters = inside length (m) × inside width (m) × fill depth (cm) ÷ 100.

If you choose an allowance, purchase volume = measured volume × (1 + allowance percentage ÷ 100). Settling is not added automatically.

Bags = purchase volume ÷ the volume printed on one bag, rounded up to a whole bag. This estimates quantity; it does not determine soil suitability or nutrient needs.

Use the same units throughout. We combine all areas before rounding the total to whole bags.

Example: a 4 × 8 raised bed

A bed measuring 4 ft × 8 ft on the inside, with 12 in left to fill, needs 32 cubic feet, or about 1.19 cubic yards. That is 16 bags at 2 cubic feet each before any optional allowance. With only 6 in left to fill, it needs 16 cubic feet, or 8 of those bags. Choose soil for your growing conditions and existing soil; there is no single blend specified by this calculator. The University of Maryland Extension source below explains different starting situations.

How we calculate

A FEW HELPFUL ANSWERS

Frequently asked questions

Know what goes into your shopping list.

Should I use inside dimensions and the full bed height?

Measure the inside length and width. Enter only the depth you still need to fill, measured from the existing material to your intended soil surface. Wall thickness, existing soil, and any gap below the rim reduce the volume compared with using the outside dimensions and full wall height.

How many bags of soil will I need?

Divide the required volume by the volume printed on your soil bag, then round the total up to a whole bag. For example, 32 cubic feet requires 16 bags at 2 cubic feet each, or 32 bags at 1 cubic foot each. Change the bag-volume input to match your product. A bag’s weight alone does not tell you its volume.

How do I work out soil for several raised beds?

Add each bed with its inside dimensions and remaining fill depth. Sum the volumes before rounding the bag count, so a partly used bag can serve another bed. For identical beds, you can also multiply the volume of one bed by the number of beds before calculating bags.

Does the calculator allow for soil settling?

No settling allowance is added automatically. The estimate is the geometric space you enter; actual material can settle or vary in moisture and density. If you choose extra material, enter an explicit allowance. This does not predict how much a particular soil mix will settle.

Formula references & useful reading

Our calculations use geometric volume and the bag volume you enter. Material selection and settling depend on your project.