Square Feet to Cubic Yards Converter
Turn a flat area into an order-ready volume. Enter square feet and a depth in inches or feet, and get cubic yards, cubic feet, and how far one yard spreads at that depth.
Example: with Area (square feet) 400 · Depth 4 · Depth unit inches → Volume: 4.94 cu yd.
- Cubic feet133.3 cu ft
- Coverage check1 cu yd covers 81 sq ft at this depth
Computed by the calculator below using its default values. Change any input to see your own numbers.
Square feet alone cannot become cubic yards — you need a depth. Cubic yards = sq ft × depth(ft) ÷ 27.
Area needs a depth to become volume
Square feet measure a surface; cubic yards measure the material piled on it. The bridge is depth: multiply area by depth in feet to get cubic feet, then divide by 27 (a yard is 3 × 3 × 3 feet). A 400 sq ft patio slab poured 4 inches thick is 400 × 0.333 = 133 cubic feet, which is 4.94 cubic yards — a supplier would round that to a 5-yard order, or more with waste.
Depth is where orders go wrong, because materials are specced in inches while the formula wants feet. This converter takes inches directly and divides by 12 for you.
Typical depths by material
If you are not sure what depth to enter: mulch beds run 2–3 inches, decorative gravel 2–3 inches, compacted gravel base under a slab or pavers 4 inches, residential concrete slabs 4 inches (6 for driveways that see trucks), and new topsoil for a lawn 4–6 inches. The coverage line in the results flips the math around — at 4 inches, one cubic yard spreads over 81 square feet, a handy sanity check when the delivery truck shows up.
How it’s calculated
Cubic yards = area(sq ft) × depth(ft) ÷ 27, with inches converted at 12 in = 1 ft. Cubic feet = area × depth(ft). Coverage = 27 ÷ depth(ft) sq ft per cubic yard. All conversions are exact; no waste factor is applied.
Assumes uniform depth over the whole area — sloped or crowned pours and uneven subgrade need extra material, so add 5–10% when ordering.
How far one cubic yard spreads
| Depth | Coverage per cu yd |
|---|---|
| 1 in | 324 sq ft |
| 2 in | 162 sq ft |
| 3 in | 108 sq ft |
| 4 in | 81 sq ft |
| 6 in | 54 sq ft |
| 12 in | 27 sq ft |
Computed as 27 cu ft ÷ depth in feet; exact.
Common mistakes
- Forgetting the depth entirely — square feet cannot convert to cubic yards without one.
- Entering inches but leaving the unit on feet, inflating the order 12×.
- Dividing square feet by 27 directly (27 converts cubic feet, not square feet).
- Ordering the exact computed volume for concrete — crews want 5–10% margin so the pour never runs short.
Frequently asked questions
What is the square feet to cubic yards formula?
Cubic yards = square feet × depth in feet ÷ 27. With depth in inches: sq ft × inches ÷ 12 ÷ 27. Example: 400 sq ft at 4 inches = 400 × 4 ÷ 12 ÷ 27 = 4.94 cu yd.
How many square feet does a cubic yard cover?
Depends on depth: 324 sq ft at 1 inch, 108 at 3 inches, 81 at 4 inches, 54 at 6 inches. Divide 324 by the depth in inches for any other figure.
Can I convert square feet to cubic yards without a depth?
No — they measure different things. Area is two-dimensional and volume is three-dimensional, so every conversion needs a thickness. Even a thin veneer of material has one.
How many cubic yards for a 400 sq ft concrete slab?
At the standard 4-inch residential thickness, 4.94 cubic yards. Most contractors order 5.5 yards to cover uneven subgrade and spillage, since a short pour is far more expensive than a little extra concrete.