Concrete is sold by the cubic yard. One cubic yard of concrete measures 3 feet by 3 feet by 3 feet (3 X 3 X 3), or 27 cubic feet. Estimating the number of cubic yards of concrete needed for a 5inchthick driveway is a matter of estimating the number of cubic inches of concrete, dividing that by 1,728 (the number of cubic inches in 1 cubic foot) to find the number of cubic feet of concrete, and then dividing that amount by 27 to determine the number of cubic yards. It sounds complicated, but it's really fairly simple. Always order slightly more concrete than you think you will need, as it can be timeconsuming to order extra concrete in the middle of a job.
Things You'll Need
 Measuring tape
 Calculator
 Pencil
 Paper

Measure the length of your driveway in inches and record that measurement.

Measure the width of your driveway in inches and record that measurement. If the width of your driveway will vary, use the average width. Remember that you are estimating, so exact figures are not required. If there is any question about the average width, be slightly generous in your estimate because it is better to order a little too much concrete than it is to order too little.

Multiply the length of the driveway by the width and then multiply that product by 5 (the number of inches thick your driveway will be). Use a calculator to do the math and perform all calculations twice to check your results. The resulting product is the number of cubic inches of concrete.

Divide the number of cubic inches by 1,728 (the number of cubic inches in 1 cubic foot). Again, use a calculator and doublecheck your results. The result is the number of cubic feet of cement.

Divide the number of cubic feet by 27 (the number of cubic feet in 1 cubic yard). Doublecheck your result. The result is the number of cubic yards of cement you will need to order to complete your driveway.
Tips & Warnings
 An example: Say your driveway is 720 inches long and 180 inches wide. Multiply 720 inches by 180 inches. The result is 129,600 square inches. Now multiply 129,600 by 5 (the number of inches thick your driveway will be). The product of the two is 648,000 cubic inches. Divide by 1,728 (the number of cubic inches in 1 cubic foot). The result is 375 cubic feet. Now simply divide 375 by 27 (the number of cubic feet in 1 cubic yard). The result is 13.88 cubic yards. You would order 14 cubic yards of concrete to insure having enough concrete to complete the job.
References
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