Finding the volume of gravel needed for your driveway can be a confusing matter. Various sources give conflicting information, and all of it hinges on your assumed knowledge of the math behind it. With the right steps you'll be able to confidently calculate how many tons of gravel you'll need.
Calculating the Square Footage of Your Driveway.
If your driveway is rectangular, use your tape measure to find the length and the width. Make both of these measurements in feet.
If your driveway is curved, use string to measure each side of your curved driveway (the inside curve and the outside curve).
Measure the length of each string in feet.
Average the two lengths. Add the two lengths together (inside curve and outside curve). Divide this number by 2. This is the average length of your curved driveway.
Multiply your driveway length by its width. This will give you the square footage of your driveway.
Calculating the Volume of Gravel You'll Need
Dig to find out how deep you'll need the gravel to be. A good rule of thumb is to dig down until you hit clay. This can vary anywhere from 2 to 8 inches.
Divide your depth measurement by 12 to convert it into feet. This will be a decimal. You can round this to one decimal place. (Example: A depth of 8 inches would be 0.6666 feet, or just 0.7 feet.)
Multiply your depth by the square footage of your driveway. This will give you the number of cubic feet of gravel you'll need.
Convert your cubic feet into cubic yards by dividing by 27. Again, you can round your answer to a single decimal point.
Calculate the number of tons of gravel you'll need by multiplying your cubic yards by the density The most common gravel used for driveways is 2-inch crusher run. This is gravel that has been crushed so that only 2-inch material remains. This has a density of 1.35 tons per cubic yard. If you use a different gravel, you'll need to use the density for that gravel.
About this Author
Tim Kane teaches sixth grade in Southern California with a master's degree in English. He has written questions for standardized tests in math, science, history, and literature. He has published articles for Verbatim as well as a book, "The Changing Vampire of Film and Television."