You need to determin how many qubic feet you have, not square feet. Here is how you do it..

Step1

measure the overall dimensions of your patio or concrete form. First take the width and then the length measurement. Next you will have to measure the depth of the form. Patios are generally about 4 inches deep. As you calculate the measurements, keep in mind you are thinking of a cube.

Step 2

Convert the depth measurement into feet, as all concrete is sold by the cubic yard, which is the same as 27 cubic feet. In order to convert any inch measurement to feet simply divide the inch measurement by 12. For the 4-inch thick patio, this would be 4 divided by 12, equal to .3333 or, for the sake of calculating, .33 feet. If the width or length measurement comes out to 10 feet and four inches, the overall foot measurement would be 10.33 feet.

Step 3

Multiply all three of the measurements together. As an example, let's say the patio you want to pour concrete in is 12 feet wide by 14 feet long, and is 4 inches deep. Multiply 12 feet times 14 feet, which is equal to 168 square feet. Then multiply by the third measurement, .33 feet, to get 55.44 cubic feet.

Step 4

Divide the cubic foot measurement by 27 cubic feet. Twenty-seven cubic feet is the volume of a cubic yard of concrete. One yard is equal to 3 feet. To calculate how much concrete is needed for your patio you need only to divide the cubic feet by 27 cubic feet per yard.

Step1

measure the overall dimensions of your patio or concrete form. First take the width and then the length measurement. Next you will have to measure the depth of the form. Patios are generally about 4 inches deep. As you calculate the measurements, keep in mind you are thinking of a cube.

Step 2

Convert the depth measurement into feet, as all concrete is sold by the cubic yard, which is the same as 27 cubic feet. In order to convert any inch measurement to feet simply divide the inch measurement by 12. For the 4-inch thick patio, this would be 4 divided by 12, equal to .3333 or, for the sake of calculating, .33 feet. If the width or length measurement comes out to 10 feet and four inches, the overall foot measurement would be 10.33 feet.

Step 3

Multiply all three of the measurements together. As an example, let's say the patio you want to pour concrete in is 12 feet wide by 14 feet long, and is 4 inches deep. Multiply 12 feet times 14 feet, which is equal to 168 square feet. Then multiply by the third measurement, .33 feet, to get 55.44 cubic feet.

Step 4

Divide the cubic foot measurement by 27 cubic feet. Twenty-seven cubic feet is the volume of a cubic yard of concrete. One yard is equal to 3 feet. To calculate how much concrete is needed for your patio you need only to divide the cubic feet by 27 cubic feet per yard.