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How Much Concrete Do I Need? Concrete Calculator for Slabs & Footings

How Much Concrete Do I Need? Concrete Calculator for Slabs & Footings Concrete is calculated in cubic yards. For a 4-inch thick slab, you need approximately 1.23 cubic yards per 100 square feet. A typical 10×10 patio slab requires about 1.3 cubic yards of concrete, or approximately thirty 80-pound bags if mixing by hand. On a typical 12x20-foot driveway extension, the formula calculates 3.3 cubic yards, but ordering 3.75 to account for uneven ground is the safer call. The total comes to $565 in ready-mix concrete, and that extra often gets used in full -- subgrade low spots can swallow nearly half a yard more than the formula predicts. That gap is why rounding up matters more than any waste percentage chart. Use our Concrete Calculator(/construction/concrete-calculator) to get precise quantities for slabs, footings, columns, and more. !Concrete volume calculator showing cubic yards needed for common slab sizes including patio, sidewalk,...