Square feet on their own cannot become cubic yards. You need one more number than most people expect: how deep the material will go. Give the area a depth, and the conversion takes one line.

To convert square feet to cubic yards, multiply the square feet by the depth in inches and divide by 324.

The square feet to cubic yards calculator below does that for you, takes square yards as well, and runs in reverse to show how much ground an order will cover.

Square feet measure a flat surface and cubic yards measure a volume, so the missing piece is always thickness. Here is how to calculate cubic yards from square feet by hand:

Measure the Area in Square Feet

Multiply length by width for a rectangle. If the area is already on a plan or a quote, use that figure; it is the starting point for every square feet-to-cubic yards conversion. For an area in square yards, multiply by 9 to get square feet, or use the square yard formula further down.

Decide the Depth in Inches

Choose the finished thickness of the layer once it is spread, and keep it in inches. The 324 formula is built for inch depths, which is how most beds, paths, and bases are specified.

Divide by 324

cubic yards = square feet × depth in inches ÷ 324

If you would rather work in feet, convert the depth to feet and divide by 27 instead. Iowa State University Extension uses that route in its mulch guide, and both give the same result: its example of 265 square feet at 1.5 inches comes to 1.22 cubic yards either way.

324 is not a rule of thumb. It is the number of square feet that one cubic yard covers at exactly 1 inch deep, and it follows from two fixed facts:

• A cubic yard holds 27 cubic feet (3 × 3 × 3), as defined in NIST Handbook 44.
• One inch is 1/12 of a foot.

27 cubic feet ÷ 1/12 foot = 27 × 12 = 324 square feet

Spread one cubic yard 1 inch thick, and it covers 324 square feet, roughly an 18 by 18 foot square. Spread it 2 inches thick, and it covers half as much. So the cubic yards an area needs are its square feet times the inches, divided by the 324 square feet that one yard covers at 1 inch. That is the whole formula, and the reason square feet to cubic yards never needs a lookup chart. For why a cubic yard holds 27 cubic feet in the first place, see our cubic feet to cubic yards guide.

Here is a square feet to cubic yards conversion for a 4-inch gravel base under a 300 square foot patio:

300 × 4 ÷ 324 = 3.70 cubic yards

Check it the long way. Four inches is a third of a foot, so 300 × 1/3 = 100 cubic feet, and 100 ÷ 27 = 3.70 cubic yards. Round up to 4 yards for the order. Loose stone settles when it is compacted, so for a compacted base, ask the supplier how much extra to allow.

If the stone is sold by weight, 3.70 yards of 3/4 inch gravel comes to roughly 4.7 to 6.3 tons using our tons per yard ranges.

At 3 inches deep, 1,000 square feet needs 9.26 cubic yards. The table converts sq ft to cubic yards for other common areas and depths:

Every cell uses the same square feet-to-cubic-yards formula: square feet × inches ÷ 324, rounded to two decimals. Round up to your supplier’s step when you order.

Turf, carpet, and some site plans measure area in square yards. A square yard is 9 square feet, so the divisor drops from 324 to 36:

cubic yards = square yards × depth in inches ÷ 36

50 square yards at 3 inches is 50 × 3 ÷ 36 = 4.17 cubic yards. Estimates sometimes shorten square yards to cubic yards as sy to cy, the same way square feet becomes sf to cy. The calculator above takes square yards directly with its SQ YD button.

To see how far an order will stretch, convert cubic yards to square feet by running the formula backwards:

square feet = cubic yards × 324 ÷ depth in inches

Five cubic yards spread 3 inches deep covers 5 × 324 ÷ 3 = 540 square feet, about a 23 by 23 foot area.

How Many Square Feet Are in a Cubic Yard?

On its own, a cubic yard has no square footage; it depends on how thick you spread it. To answer how many square feet are in a cubic yard, divide 324 by the depth in inches: 324 square feet at 1 inch, 108 at 3 inches, 54 at 6 inches. The calculator’s "Cubic yards to area" mode does this for any depth.

Most square feet to cubic yards errors come from one of these:

• Dividing square feet by 27 with no depth. 300 ÷ 27 = 11.1 describes nothing, because there is no volume until a depth is added.
• Using inches in the 27 formula. 300 × 4 ÷ 27 gives 44.4 "cubic yards" for a patio base that needs 3.70. Pair inches with 324, or feet with 27.
• Treating square yards as cubic yards. 50 square yards is an area. Multiply by the depth in inches and divide by 36 before calling it a volume.

Square feet to cubic yards comes down to one extra measurement and one fixed number. Keep these three formulas handy:

• Square feet to cubic yards: square feet × inches ÷ 324.
• Square yards to cubic yards: square yards × inches ÷ 36.
• Cubic yards to square feet covered: cubic yards × 324 ÷ inches.

If you have length and width rather than square footage, or several shapes to add together, use the main cubic yard calculator next.