TOPSOIL
Topsoil calculator
Cubic yards of topsoil = square feet × depth in inches ÷ 324. That is the whole calculation. Enter your area and the depth you intend to fill, and the number you get is the volume the supplier will quote in. Everything below is the bag conversion, the weight, and the two places topsoil differs from mulch.
Worked example
A 120 sq ft bed filled to 4 inches: 120 × 4 ÷ 324 = 1.48 cubic yards. In cubic feet that is 120 × 4 ÷ 12 = 40 cubic feet.
Bags are sold whole, so divide by the bag volume and round up. At the common 0.75 cubic foot bag, 40 ÷ 0.75 = 53.3, so 54 bags. The same volume in 1 cubic foot bags would be 40 bags, and in 1.5 cubic foot bags 27.
That spread is the reason to read the bag before ordering: on this bed, the difference between a 0.75 and a 1.5 cubic foot bag is 27 bags of carrying.
Bag volumes topsoil actually comes in
Bagged topsoil is sold in smaller volumes than bagged mulch, because it is heavier per cubic foot. The size that appears most often on retail listings is 0.75 cubic feet; 1 and 1.5 cubic foot bags also exist, and larger bags are usually labelled as soil conditioner or raised-bed mix rather than topsoil. Use the number on your bag — the arithmetic above only holds for the bag you actually buy.
Why topsoil is heavier than mulch for the same yard
Topsoil is mineral, not woody, so a cubic yard weighs considerably more than the 450 to 850 lb range published for organic mulch (University of Regina, Math Central). The practical consequence is about transport, not arithmetic: a single cubic yard of topsoil is at the edge of what a half-ton pickup should carry, and a few yards is a delivery rather than a series of car trips. Ask the supplier for the weight of their product rather than assuming a figure — density varies with moisture and with how much organic matter is blended in.
Depth is your decision, and it is not the same as mulch depth
Mulch sits on top of existing soil as a cover layer, which is why the published range for mulch is 2 to 4 inches. Topsoil is usually being used to create or raise a growing layer, so the depth is set by what you are planting into and how much root room the plants need — a figure that belongs to your planting plan or your extension service, not to a calculator. Measure the depth you actually need, then put that number into the formula above.
How much topsoil for a raised bed?
A raised bed is a box, so the calculation is a fill: cubic feet = bed square feet × fill depth in inches ÷ 12. A 4 ft × 8 ft bed is 32 sq ft, so filling it 6 inches deep takes 32 × 6 ÷ 12 = 16 cubic feet, and filling it 12 inches takes 32 cubic feet, which is 1.19 cubic yards. In 0.75 cubic foot bags that is 22 bags for the 6-inch fill and 43 for the 12-inch fill.
Two things decide the depth rather than the arithmetic. First, what you are filling: a bed built on existing soil may only need the top few inches improved, while a bed standing on concrete or gravel needs its whole rooting depth brought in. Second, whether you are filling with pure topsoil or with a topsoil-and-compost blend — a blend settles as the organic part decomposes, so the loose depth you order is not always the depth you keep. Decide the depth from what you are planting, then run it through the formula.
Common ordering mistakes
- Ordering by bag count instead of volume. Work out cubic feet or cubic yards first, then convert; a bag count chosen first is a guess.
- Assuming a bag size. Check whether the listing means 0.75, 1 or 1.5 cubic feet.
- Forgetting that the soil settles. Loose topsoil compacts after watering and settling; if you are filling to a finished grade, tell the supplier what the loose material has to settle to.
- Treating topsoil and compost as interchangeable. They are not, and the compost calculator gives a different answer for the same bed.
Related calculators
The mulch calculator uses the same engine for a cover layer, and the coverage calculator subtracts a bare circle from a rectangular bed — the same subtraction applies to a topsoil bed with a tree in it. For switching between cubic feet and cubic yards, the bag conversion page shows the arithmetic.
Sources: Bag volume is 0.75 cubic feet, the common retail size for bagged topsoil. Mulch weight range from University of Regina, Math Central, read 2026-09-21.
Cite this dataset
The mulch coverage, bag-count and dated price tables from this site are archived as a citable dataset: Mulch coverage, bag-count and dated bulk price tables, version v1, published 20 September 2026, 9 files, creator ERTHK — DOI 10.5281/zenodo.22855990, record at zenodo.org/records/22855990.
Released under CC0 1.0 Universal (Creative Commons Zero v1.0 Universal): free to copy, modify and redistribute.
The source library that generates the tables, with its test suite, is at github.com/ERTHK/mulch-measure-calculator-kit, released under the MIT license.