Determining how much concrete is necessary for a straight driveway is a fairly simple task. A tape measure, a calculator and a few minutes of time will give you the answer you need fairly quickly. This task becomes more challenging when there is a curve, or radius, in the driveway. It is very important that you are accurate with your calculations because you pay for what you order, so you don't want extra. Not enough is also a problem because you get the best results when completing the pour in one shot. Knowing how to calculate with a curve can solve many problems.
Calculate How Much Concrete is Needed for a Curved Drive
Start by drawing out the driveway on a piece of paper. Try to make it close to scale, but being exact is not critical.
Locate where the driveway will be positioned. Break it up into square or rectangular sections using a chalk line. Measure the length and width of these sections and record them in the drawing. Your drawing should be broken into straight and curved sections and you should have measurements for all of the straight parts.
For each straight section, multiply the length times the width. This will give you the square footage of this section. Add the square footage of each straight section together so you have the total square footage of the straight sections of the driveway.
Measure both the long and short sections of the curved part of the path. This could also be called the outside and inside parts of the path. Record your measurements in your drawing. Add these two lengths together and divide it by 2. Basically, what you are doing is pretending the curved sections are actually straight. The width of the curved section should be the same as the straight section, so multiply the width times the average of the two lengths. This will give you the square footage of the curved section.
Add the square footage of the straight sections to the square footage of the curved sections to give you the square footage of the entire drive. To calculate how much concrete you need, factor in the depth of the concrete. A standard depth is 3 to 4 inches. Multiply this depth times your total square footage. This will give you the cubic feet and how much concrete you will need. It is a good idea to add about 5 percent to this number so you have a little extra.