Short answer: One cubic yard of concrete covers 81 square feet at 4 inches thick, 65 square feet at 5 inches and 54 square feet at 6 inches. The rule is 324 divided by the thickness in inches.
| Thickness | Area covered by 1 cubic yard | Yards for 100 sq ft | Yards for 1,000 sq ft |
|---|---|---|---|
| 2 in | 162 sq ft | 0.62 | 6.2 |
| 3 in | 108 sq ft | 0.93 | 9.3 |
| 4 in | 81 sq ft | 1.23 | 12.3 |
| 5 in | 64.8 sq ft | 1.54 | 15.4 |
| 6 in | 54 sq ft | 1.85 | 18.5 |
| 8 in | 40.5 sq ft | 2.47 | 24.7 |
Where 324 comes from
A cubic yard is 27 cubic feet. Spread 1 foot deep, it would cover 27 square feet. A slab is measured in inches, and there are 12 inches in a foot, so a slab t inches thick covers 27 times 12 divided by t square feet, which is 324 divided by t.
At 4 inches, which is the usual thickness for a patio or walkway, that gives 81 square feet. Thinner slabs go further and thicker ones less so, but the relationship is exact only for a perfectly level pour.
Plan for extra
In practice the ground is never perfectly flat and forms bulge a little. Add 5 to 10 percent to the volume, and never order to the exact figure. Running out of concrete halfway through a pour makes a weak joint, while a little too much costs very little.
Worked example
A patio 12 ft by 15 ft has 180 square feet. At 4 inches thick it needs 180 divided by 81, which is 2.22 cubic yards. With 10% extra that is 2.44, so order 2.5 cubic yards.
Use the Concrete CalculatorEnter your own measurements and get an exact amount.
Frequently asked questions
How many square feet does 1 yard of concrete cover at 6 inches?
54 square feet.
How many yards of concrete do I need for 1,000 square feet?
About 12.3 cubic yards at 4 inches thick, and 18.5 at 6 inches, before the extra for waste.
How many square feet does half a yard cover?
About 40.5 square feet at 4 inches thick.
How many bags of concrete cover the same area?
It takes about 45 bags of 80 lb mix to make one cubic yard, so 45 bags cover about 81 square feet at 4 inches thick.
More quick answers
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Related calculators
Figures are typical planning values. Material sizes, densities and local requirements vary, so confirm with your supplier before ordering.
Last updated October 11, 2026.