How to Size Concrete

Measure the length and width of your rectangular driveway from the front edge of the apron to your garage. This section of concrete needs to be 4 inches thick. Multiply the length and width by the thickness to determine the square footage needed. For example, the area of a driveway that is 8 feet wide by 20 feet long will be calculated as 8 (width) times 20 (length) times 4 (depth) for an area of 640 square feet of concrete.

Divide an oval or odd-shaped driveway into sections. Measure the length and width of each section. Sketch the driveway onto graph paper, treating each square on the paper as 1 foot and using your section measurements to obtain an accurate reading. Count the number of whole and over-half-filled squares as 1 foot of concrete, and each less-than-half-filled square as 6 inches. Multiply by the thickness required – 4 inches – to get the square footage. For example, the square footage of an oval driveway made up of 30 full squares and 16 half ones is calculated as 30 (full squares) plus 8 (16 half-squares divided by 2 to get an amount of full squares) times 4 (depth required) to equal 152 square feet of concrete.

Measure the driveway apron separately. Divide the apron into sections as described in step two, since aprons aren't a perfectly shaped square. Measure the length and width of each section, and then sketch the apron onto graph paper. Count the squares, and then multiply by 6, as concrete aprons need to be 6 inches deep. For example, an apron, sketched out onto graph paper that measures 8 full squares and 4 half squares, has its square footage calculated as 8 (full squares) plus 2 (4 half squares divided by 2 to get an amount of full squares) times 6 (required depth) to equal 40 square feet of concrete.