How Much Topsoil Do I Need? Cubic Yards, Depth, Weight and Bags

Cubic yards of topsoil = length (ft) × width (ft) × depth (in) ÷ 12 ÷ 27. A 4 × 8 ft raised bed filled 12 in deep takes 32 cubic feet, or 1.19 cubic yards: about 1.3 tons at 1.1 tons per yard.

One cubic yard covers 324 sq ft at 1 in deep, 108 sq ft at 3 in and 54 sq ft at 6 in. The depth is the part you decide, so this guide gives the math and then shows what extension services say about depth for lawns and raised beds.

How do you calculate how much topsoil you need?

cubic feet  = length (ft) × width (ft) × depth (in) ÷ 12
cubic yards = cubic feet ÷ 27
            = area (sq ft) × depth (in) ÷ 324        (324 = 27 × 12)
tons        = cubic yards × tons per cubic yard
order       = net cubic yards × (1 + settling allowance)

1. Measure the area to fill in square feet. For a bed or lawn that is not a rectangle, split it into rectangles and circles, or use the square footage calculator.
2. Decide the depth of soil you want in inches. Use the depth of the soil, not the height of a frame or board.
3. Multiply area by depth, then divide by 324 for cubic yards.
4. Add a settling allowance and round up. Convert to tons or bags only if you buy that way.

The 27 is cubic feet per cubic yard, and the 12 turns inches into feet. Texas A&M AgriLife Extension (Travis County) gives the same formula: “Total cubic yards = (Length feet * Width feet * (Depth inches / 12)) / 27”. If you want the volume of other shapes, see how to calculate cubic yards.

Quick table: how far does a cubic yard of topsoil go?

These are pure geometry, so they apply to any loose material spread at a level depth. The right-hand columns show how much to order for 100 and 1,000 sq ft.

How deep should topsoil be?

There is no single depth: it depends on what you are building. Where an extension service gives a figure, it is below. Where none could be found, the depth is yours to choose and the table above does the math.

Three limits on that table. The Penn State figure is for establishing turf and is a firmed depth, so you add an allowance for settling on top. Existing topsoil counts, so you may only need to buy the shortfall: subtract the depth you already have from the depth you want. And the Maryland depths are for beds sitting on pavement or concrete. A bed open to the ground below may not need the same depth, so check your own state’s extension service. For topdressing, overseeding or filling low spots, no extension depth was found for this guide: use the depth your project needs and the formula above.

Worked examples: a raised bed and a lawn

• Raised bed, 4 × 8 ft, 12 in of soil. Volume: 4 × 8 × (12 ÷ 12) = 32 cubic feet, and 32 ÷ 27 = 1.185 cubic yards.
• With a 10% settling allowance: 32 × 1.10 = 35.2 cubic feet, and 35.2 ÷ 27 = 1.304 cubic yards. Rounded up for ordering, that is about 1.3 yards, or 1.5 if the supplier sells by the half yard.
• Weight at 1.1 tons per cubic yard: 1.304 × 1.1 = 1.43 tons.
• Lawn, 1,000 sq ft, 4 in firmed depth. 1,000 × 4 ÷ 324 = 12.35 cubic yards. With a 10% allowance, 12.35 × 1.10 = 13.58 cubic yards.
• The same lawn at 6 in: 1,000 × 6 ÷ 324 = 18.52 cubic yards, or 20.37 with 10%.

The 10% allowance is an editable convention used by the calculator on this site, not a standard. Raise it for a deep fill or loose, compost-rich soil.

How much does a cubic yard of topsoil weigh?

Weight varies with moisture and organic content, so it is the least certain number in this guide. These starting values come from calculator-site and supplier-style tables, not from a standard or a lab, and they are in short tons (2,000 lb) per loose cubic yard.

Rained-on soil is heavier than the dry figure, and manufactured topsoil blended with compost is usually lighter than mineral soil. If your supplier sells by the ton, ask for their tons-per-yard figure and use it instead. Weights for gravel and other materials are in how many cubic yards are in a ton.

How many bags of topsoil do I need?

bags = ceil( cubic feet × (1 + allowance) ÷ cubic feet per bag )

Bag size is printed on the bag, so read the label. Texas A&M AgriLife Extension lists bags of 0.75, 1, 1.25 and 2 cubic feet for soil and compost. Bags per cubic yard are 27 ÷ bag size, rounded up:

For the 4 × 8 ft raised bed with a 10% allowance (35.2 cubic feet), that is 36 bags of 1 cubic foot or 47 bags of 0.75 cubic foot (35.2 ÷ 0.75 = 46.9). Past a couple of cubic yards, compare bulk delivery with bags at your own suppliers, delivery charges included. Ask them for current prices: this guide does not quote any.

Why add a settling allowance and round up?

Loose soil settles when it is watered and walked on, and ground is rarely perfectly level. Penn State states its lawn depth as a “firmed or settled depth”, which is the depth after settling, so the amount you spread must be deeper than that. A 10% allowance is a common starting point and the calculator lets you pick 0 to 25%. Many suppliers deliver in set increments, so ask what yours sell by and round the order up to it. Running short usually means a second delivery.

Assumptions, common errors and limits

• The volume math assumes a flat area filled to a level depth. Slopes, mounds and grading need a surveyed average depth or a series of smaller areas.
• Using frame height instead of soil depth. A 4 × 8 ft bed filled 12 in deep needs 1.19 cubic yards, and the same bed filled 3 in needs 0.30.
• Using dry weight for wet soil. If you buy by the ton, a rained-on pile means each ton covers less ground.
• Skipping the allowance. Fill to the depth you measure after it settles, not before.
• Reading the bag size from memory. Bags range from 0.75 to 2 cubic feet, and some are sold in liters.
• This guide estimates quantities only. It does not judge soil quality, drainage, grading or what suits your plants. Ask your local extension office about soil testing and amendments.

Common questions