Topsoil Calculator

How much topsoil an area needs

Topsoil is sold by volume, so the question «how much do I need» is a volume question: area times depth. In imperial units the whole thing collapses into one number:

That 324 is exact and worth knowing on its own. A cubic yard is 3 × 3 × 3 = 27 cubic feet; spread one inch — a twelfth of a foot — deep, those 27 cubic feet stretch over 27 × 12 = 324 square feet. So a cubic yard covers 324 ft² at 1 inch, 162 ft² at 2 inches, 81 ft² at 4 inches, and so on down the line. Nothing about soil enters this part of the calculation, which is why the volume answer is exact and the weight answer further down is not.

Step by step

1. Measure the area in square feet. Width × length for a rectangle; split anything L-shaped into rectangles and add them up.
2. Decide the depth in inches. This is your decision, not the calculator's — see the caveat below.
3. Multiply and divide by 324. Area × depth ÷ 324 gives cubic yards; area × depth ÷ 12 gives cubic feet if you are buying in bags.
4. Add about 10% for waste. Quoted from the WSDOT Design Manual, and it also absorbs the settling that follows raking and watering.

How much one cubic yard covers

This is the table people actually come for. The middle column is the coverage of a single cubic yard; the right column is what 100 square feet would take at that depth.

Common areas and what they take

Every row here has its own page with the depth table, the weight and the ordering figure worked out. All of them assume 4 inches.

What topsoil weighs, and why we print a range

Penn State Extension gives a dry silt loam a bulk density of 1.33 g/cm³, which works out to 82.99 lbs per cubic foot and 2,241 lbs per cubic yard. The same source immediately qualifies it: sandy soils are denser than that and organic soils lighter. It does not put numbers on either end, so we print 2,000–2,500 lbs per cubic yard — a band around the sourced figure, declared as our own allowance rather than a measurement.

How much to order, and in what

• Bulk, by the cubic yard. The figure this page gives you. Add the 10% and round up to whatever increment your supplier delivers in.
• Bulk, by the ton. Some yards quote by weight instead. Use the weight band, and ask which state it is quoted in — dry, damp, loose or compacted all give different numbers for the same pile.
• Bags. Bagged topsoil prints its volume on the bag, so divide the cubic-feet figure by that number. Bags stop making sense somewhere around a cubic yard: 27 cubic feet is a lot of bags to carry.
• The 10% itself. «If material is to be stockpiled, increase required quantities by 10% to allow for waste» — WSDOT Design Manual. It is a road-building manual, but the arithmetic of waste is the same in a garden.

Where this stops being exact

• The default depth is an assumption. The form starts at 4 inches, and that is our choice, not an extension-service recommendation. Mulch has published depths; topsoil, as far as we could find, does not. Dressing a lawn takes far less than filling a new bed.
• The weight is a band, not a figure. Bulk density moves with texture, organic matter and moisture. The volume answer above does not depend on any of that; the weight answer depends on all of it.
• Loose soil settles. A bed filled level today sits lower after the first watering. The 10% allowance covers waste, not settlement — for a bed that has to stay level, plan on topping it up.
• Screened and unscreened are not the same product. Screened topsoil is what most volume calculators implicitly assume; a load with clods and stones fills the same space differently.
• Area first. If you have measurements rather than an area, the square footage calculator turns width and length into the number this page wants.