Topsoil, Compost and Garden Soil Calculator

How it works

The area is length × width in square feet. Multiplying by the depth, converted from inches to feet, gives the volume in cubic feet, and dividing by 27 gives cubic yards, the unit bulk soil, compost and sand are sold in. One cubic yard spread 1 in deep covers 324 sq ft; at 3 in it covers 108 sq ft.

Suppliers often quote or load by weight, so the volume is also shown as a weight range. Each material has a typical range of pounds per cubic yard for loose material, taken from supplier and material guides; the volume times each end of the range, divided by 2,000 lb per ton, gives the low and high tonnage. The material changes only the weight, never the volume or bag count. Choosing Custom uses a single weight per cubic yard instead, such as the figure on a supplier's ticket.

Bagged soil and compost are sold by volume, so the bag count is the cubic feet divided by the bag size, rounded up to whole bags.

Formula

area        = length × width                       (sq ft)
cubic feet  = area × depth (in) ÷ 12
cubic yards = cubic feet ÷ 27
tons        = cubic yards × weight (lb per cu yd) ÷ 2,000
bags        = ⌈ cubic feet ÷ bag size ⌉
typical lb per cu yd: topsoil and fill 2,000–2,700; compost 1,000–1,300;
                      sand 2,700–3,300; garden-soil blend 1,000–2,700

Example

A 10 ft × 10 ft bed covered 3 in deep is 100 sq ft × 0.25 ft = 25 cu ft, or 25 ÷ 27 = 0.93 cu yd. As topsoil at a typical 2,000–2,700 lb per cu yd that is about 0.93 to 1.25 tons; in 1 cu ft bags it is 25 bags.

The same bed in compost at 1,000–1,300 lb per cu yd weighs about 0.46 to 0.60 tons. The volume and the 25 bags do not change.

Assumptions and limitations

• The area is a rectangle covered to an even depth. An irregular area can be split into rectangles and the results added.
• Weights are typical published ranges for loose material, not measurements of any particular load. Moisture alone can change the weight of soil, compost or sand by about 30% either way, and the supplier's own figure for the material delivered is the one that applies.
• Fill dirt is given the topsoil range because both are mineral soil. A garden-soil blend is a mix of topsoil and compost, so its weight lies between theirs; the range shown spans the two.
• Soil and compost settle after spreading and after the first watering, so the finished depth is usually less than the depth spread. No allowance is made for settling or spillage.
• Bag sizes are nominal volumes as packed.
• Bulk material is usually sold in whole or half cubic yards, often with a minimum delivery.

Frequently asked questions