How many square feet does a yard of concrete cover?
One cubic yard covers 81 square feet at 4 inches thick, 54 square feet at 6 inches, or 108 square feet at 3 inches. Thickness changes the answer.
Quick answer: 1 cubic yard = 81 square feet at 4 inches
A “yard” of delivered concrete means one cubic yard (27 cubic feet), not a square yard. The square footage changes with how deep you place the concrete: 1 yd³ can cover 81 ft² at 4 in, 64.8 ft² at 5 in, or 54 ft² at 6 in before any extra allowance. These are theoretical geometric volumes, assuming perfectly uniform depth.
Square feet per yd³ = 27 ft³ ÷ (thickness in inches ÷ 12) = 324 ÷ thickness in inchesExample: 324 ÷ 4 = 81 sq ft. At 6 inches: 324 ÷ 6 = 54 sq ft. A 6-inch layer uses 50% more concrete than a 4-inch layer over the same area; this page estimates quantities, not which layer is appropriate or safe.
Concrete coverage chart by thickness: 2 to 12 inches
Use the chart to convert a known number of cubic yards into a theoretical surface area. The “100 ft²” column works in the opposite direction, giving the exact geometric yardage before overfill or waste. Thickness examples are math scenarios, not building-code or structural recommendations.
| Uniform thickness | 1 yd³ covers | 2 yd³ cover | Yards needed for 100 ft² |
|---|---|---|---|
| 2 in | 162.00 ft² | 324.00 ft² | 0.62 yd³ |
| 3 in | 108.00 ft² | 216.00 ft² | 0.93 yd³ |
| 3.5 in | 92.57 ft² | 185.14 ft² | 1.08 yd³ |
| 4 in | 81.00 ft² | 162.00 ft² | 1.23 yd³ |
| 5 in | 64.80 ft² | 129.60 ft² | 1.54 yd³ |
| 6 in | 54.00 ft² | 108.00 ft² | 1.85 yd³ |
| 8 in | 40.50 ft² | 81.00 ft² | 2.47 yd³ |
| 10 in | 32.40 ft² | 64.80 ft² | 3.09 yd³ |
| 12 in | 27.00 ft² | 54.00 ft² | 3.70 yd³ |
Keep calculations unrounded until the final displayed answer or purchase quantity. When combining several zones, add their actual volumes before applying any extra-material allowance.
Convert cubic yards into square feet — or square feet into cubic yards
This estimator gives both directions at once. It does not infer a safe slab thickness, supplier minimum, delivery fee or bag yield. Enter the thickness already selected for your project.
Worked example: a 10 × 10 ft slab at 4 inches
First measure the area: 10 × 10 = 100 ft². At 4 inches, the required geometric volume is 100 × 4 ÷ 324 = 1.23457 yd³. A hypothetical 10% extra-material allowance gives 1.23457 × 1.10 = 1.35802 yd³, displayed as 1.36 yd³. Do not automatically round up to 1.5 cubic yards: a ready-mix supplier may have different minimums, increments and fees. Ask for a quote using your actual order volume.
At 6 inches, the same 100-square-foot footprint requires 100 × 6 ÷ 324 = 1.85185 yd³ before any allowance. Thickness changes volume, not the project’s square footage. If you need a slab-size table, use the 8×8 to 30×30 ft slab reference; if you have corners, step-downs or multiple pads, use the multi-section slab calculator.
Why cubic yards and concrete bags are different questions
Concrete delivered by a ready-mix truck is measured by volume in cubic yards. Packaged concrete is sold by bag weight, and each exact mix produces an approximate yield in cubic feet per bag. You cannot turn a square-foot area directly into a bag count without a thickness and a real product yield.
For example, QUIKRETE Concrete Mix No. 1101 reports approximately 0.60 ft³ per 80 lb bag. One 80 lb bag theoretically covers 0.60 ÷ (4 ÷ 12) = 1.8 ft² at 4 inches, before additional material. Use the bag purchase planner for your specific slab dimensions, weight handling and supplier prices.
If deciding whether to mix bags or order delivered concrete, read bags vs. ready-mix: quantities, dry weight, fees and delivery questions.
Three mistakes that change the area estimate
- Mixing up square yards with cubic yards: a cubic yard is volume (27 ft³); square feet describe surface area. Thickness is required to convert between them.
- Using nominal thickness instead of actual placement depth: a nonuniform subgrade, thickened edge or step-down changes the real concrete volume. Measure separate zones rather than assuming one depth everywhere.
- Counting extra material twice: if you calculated order volume with 10% additional allowance, do not also reduce coverage as if a second 10% loss applied. Keep net geometric volume and additional purchase amount separate.
This is a material-quantity conversion guide; consult applicable site specifications, building code and qualified advisers for design requirements.
Calculation basis and source checking
The exact arithmetic comes from 1 yd³ = 27 ft³ and 12 inches per foot. See our published calculation methodology and the independently reproduced seven-tool software QA examples. For conventional coverage context, see Concrete Network’s concrete yard coverage guide ↗. Bag-yield examples link to QUIKRETE's published product datasheet ↗.
Written and maintained by: Ethan Zhang, site operator. Engineering support: Enrique García, advisory contributor. Numerical unit tests verify the conversion formulas; no independent engineer signature or structural design approval is claimed. Report a calculation error.