Square Feet to Cubic Yards Calculator

How do you convert square feet to cubic yards?

Multiply the area in square feet by the depth in inches, then divide by 324. Square feet measure area only, so without a depth there is no volume to convert.

Cubic yards = square feet × depth (in) ÷ 324

The 324 comes from 12 inches per foot × 27 cubic feet per cubic yard. If you prefer two steps: square feet × depth in feet = cubic feet, then cubic feet ÷ 27 = cubic yards.

Typical depths: 4 in for a concrete patio, 2–3 in for mulch and 4–6 in for a gravel base. Split odd shapes into rectangles and add the square feet before you convert. Add about 10% for concrete, and round loose materials up because they settle.

Square feet to cubic yards chart

Each cell is square feet × depth ÷ 324, before any waste allowance.

All values are cubic yards. For a concrete slab, the concrete slab calculator adds waste and bag counts.

How many square feet does a cubic yard cover?

Divide 324 by the depth in inches. That gives the area one cubic yard covers at that depth, for any material.

To turn yards back into square feet, multiply by 324 and divide by the depth. Ten cubic yards of concrete covers 810 ft² at 4 in or 540 ft² at 6 in.

Square feet to cubic yards for concrete

Concrete is ordered in cubic yards, so this conversion is the first step of every slab estimate. At 4 in thick, each 100 ft² takes 1.23 yd³. A 1,000 ft² slab at 4 in is 12.35 yd³, or 13.58 yd³ with 10% extra. Ask your ready-mix supplier what order increment they use (for example ¼ or ½ yd³) and round up to it after adding waste.

Coverage per yard shrinks fast when the base is low. Every ½ in of extra depth over 1,000 ft² takes another 1.54 yd³, which is more than the whole 10% allowance on a 4 in slab of that size (1.23 yd³). Before you call the plant, run a string line across the forms and measure down to the base at several points. If the average depth is 4½ in rather than 4 in, use 4½ in the formula: 1,000 × 4.5 ÷ 324 = 13.89 yd³ instead of 12.35 yd³. Compare that extra concrete with the cost of raising the base with gravel from your supplier before the pour; on most jobs one of the two is clearly cheaper once you have both quotes.

For pricing, the concrete price per yard guide explains what goes into a quote. Prices vary by region, so get local quotes and enter them in the cost tools.

Square feet to cubic yards for mulch, soil and gravel

The math is the same, only the depth changes. Mulch is commonly spread 2–3 in deep (Clemson Extension), new lawns need at least 4–6 in of settled topsoil (Penn State Extension), and for gravel paths use the depth your supplier or product recommends. Gravel and stone are often sold by the ton, so convert your yards with the tons to cubic yards converter or use the gravel calculator, which does both steps.

Square metres, square yards and metric depths

• Square yards: multiply by 9 to get square feet first. 100 square yards at 4 in deep is 11.11 yd³.
• Square metres: multiply area (m²) by depth in metres to get m³. 1 m³ covers 10 m² at 10 cm, 13.3 m² at 7.5 cm and 20 m² at 5 cm.
• Mixed units: 1 ft² = 0.0929 m², and one cubic yard spread 1 in deep covers about 30.1 m².

Concrete yards to square feet

Multiply cubic yards by 324, then divide by the thickness in inches. Use it to check how far a load will go, or what is left after the main pour.

These are full-depth areas with no waste. If you ordered 10% extra, the planned area uses the base volume and the remainder is your margin for a low base or bowed forms.

Concrete square footage calculator: measuring the area

Measure the finished concrete surface, inside the forms, in feet. For a rectangle multiply length × width. For anything else, split it up:

1. L- and T-shapes: divide into rectangles that do not overlap and add them. A 20 × 12 ft patio with a 10 × 8 ft extension is 240 + 80 = 320 ft², which is 3.95 yd³ at 4 in.
2. Circles: 3.1416 × radius². A 12 ft round pad is 113.1 ft².
3. Triangles and angled corners: ½ × base × height, added to or subtracted from the rectangle around it.
4. Openings: subtract the area of anything that will not be concrete, such as a planting bed left inside the slab.
5. Gentle slopes: measure the length along the ground with the tape held level. The surface on a gentle slope is only slightly longer than its plan length, but the depth can change a lot from one end to the other, so average several depth readings.

Then apply the depth once. If different parts are different thicknesses, such as a 4 in walk joining a 6 in pad, convert each part separately and add the cubic yards.

One area, several layers

Most slabs have a base under them, and the same square footage drives every layer. Convert each layer with its own depth and order them separately, because they come from different suppliers.

Check your gravel supplier’s own tons-per-yard figure; it can differ from the typical 1.4. The tons to cubic yards converter handles other materials.

Lawn topdressing works the same way at very thin depths. 5,000 ft² of lawn topdressed ¼ in deep takes 3.86 yd³, and ½ in takes 7.72 yd³. Shallow layers like this are where using the ÷ 324 rule with fractional inches saves the most arithmetic.

Concrete slab weight per square foot

Multiply the thickness in feet by the concrete density. At the 150 lb/ft³ normal-weight figure this site uses, a 4 in slab weighs 50 lb per square foot. QUIKRETE states about 140 lb/ft³ for its bagged mix, which gives 46.7 lb per square foot at 4 in.

A 400 ft² slab at 4 in therefore weighs about 20,000 lb, or 10 US tons. This is the weight of the slab itself; whether a deck, roof or suspended floor can carry it is a question for an engineer, not a calculator.

Concrete square footage price: per yard to per square foot

Ready-mix is priced per cubic yard, but contractors and comparison sites often quote per square foot. To convert your plant’s quote, divide the price per yard by the square feet one yard covers at your thickness:

Material price per ft² = price per yd³ ÷ (324 ÷ thickness in inches)

At 4 in the divisor is 81, at 5 in it is 64.8 and at 6 in it is 54. To include a 10% waste allowance, divide by 73.64 at 4 in or 49.09 at 6 in instead. This gives the material cost only. Delivery, any small-load fee, base preparation, forms, reinforcement and finishing labour are extra and vary by region, so get local quotes. The cost to pour a concrete slab calculator adds those lines for you.

Self-leveling and thin topping coverage

Thin layers are measured in fractions of an inch, so cubic yards are the wrong unit. Work in cubic feet: one cubic foot covers 12 ft² at 1 in, so divide 12 by the thickness.

A 200 ft² floor at ¼ in needs 4.17 ft³ of mixed material, and 8.33 ft³ at ½ in. Self-leveling underlayments and resurfacers each list their own coverage per bag at a stated thickness, so divide your area by the number on the bag you are buying. Standard concrete mix is not a substitute: QUIKRETE Concrete Mix is rated for pours 2 in thick or more.

Cement needed per square foot

For a site-mixed 1:2:3 mix (cement : sand : stone by volume), a 4 in slab takes about 0.086 ft³ of cement per square foot, roughly 8 lb. At 6 in it is about 0.128 ft³, or 12.1 lb. These figures use the 1.54 dry-volume factor and treat a 94 lb bag of Portland cement as about 1 ft³, a common planning assumption rather than a manufacturer figure.

So 100 ft² at 4 in needs about 8.56 ft³ of cement, which is 9 bags of 94 lb, plus about 17.1 ft³ of sand and 25.7 ft³ of stone. Other ratios change the cement figure, and the concrete mix ratio calculator works them out. For bagged ready-to-mix concrete, the cement is already in the bag, so you only need the bag count.

Square yard concrete calculator

Plans and some flooring quotes give areas in square yards. One square yard is 9 ft², so either multiply by 9 and use the square feet formula, or use the square yard version directly:

Cubic yards = square yards × depth (in) ÷ 36

The 36 is the number of inches in a yard. 50 square yards at 4 in deep is 50 × 4 ÷ 36 = 5.56 yd³, and at 6 in it is 8.33 yd³. One square yard at 4 in is 0.111 yd³, so nine square yards at 4 in make one cubic yard.

Common mistakes when converting square feet to cubic yards

• Using the wrong depth unit. 3 in is 0.25 ft. If you multiply 500 ft² by 3 and divide by 27, you get 55.6 yd³, twelve times too much. Use ÷ 324 when the depth is in inches.
• Measuring the depth of the edging, not the layer. A bed with 6 in edging may only need 3 in of mulch on top of existing soil.
• Forgetting old material. If a bed still has 1 in of mulch, a 3 in target only needs 2 in more: 500 ft² then takes 3.09 yd³ instead of 4.63 yd³.
• Skipping the waste allowance. Concrete needs about 10% extra. A slab base that is ½ in low over 400 ft² alone adds 0.62 yd³.
• Ignoring irregular shapes. Split an L-shape into rectangles. For a circle, area is 3.1416 × radius², so a 10 ft circle is 78.5 ft², or 0.97 yd³ at 4 in deep.
• Mixing up square yards and square feet. A plan in square yards is 9 times smaller as a number. 100 square yards at 4 in is 11.11 yd³, but treating it as 100 ft² gives only 1.23 yd³.

Square feet to cubic yards vs related calculators: which one to use

• This converter when you already know the area in square feet and the depth.
• Cubic yard calculator when you are starting from length, width and depth.
• Concrete slab calculator for a concrete slab, because it adds waste, order rounding and bag counts.
• Mulch calculator or gravel calculator when you want bags or tons of a specific material, not just yards.