Whether you plan to lay a sidewalk, pour footings for a building or fence posts, create raised beds for gardening or just fill in a low-lying area with extra soil, you will need to know how much material it takes to fill the area. Both concrete and dirt typically come in cubic yards, so calculate the volume of the area you need to fill in cubic yards to find out how much material to order.
Measure the dimensions of the area you want to fill with concrete or dirt. For a rectangular plot, measure the length and width. For a round footing, measure across the circle at the widest point to get the diameter. Record the dimensions in feet -- divide inches by 12 to get feet. If a measurement is 4 feet 3 inches, for example, record it as 4 + 3/12 = 4.25 feet.
Calculate the area. Multiply length times width for a square or rectangular plot. Divide diameter by two, square the result and multiply by 3.14 for a circular area. For example, the area of a rectangle 10 feet wide by 5 feet long is 105 = 50 square feet. The area of a circle 2 feet in diameter is 3.14(2/2)^2 = 3.14 square feet.
Measure the depth of the hole you need to fill, or the thickness you want if the material will be above ground -- in a raised flowerbed, for example. Record the measurement in feet; if you want to pour a sidewalk 6 inches deep, for example, the depth is 6/12 = 0.5 feet.
Multiply the depth by the area to get the volume you need to fill. For a 50-square-foot plot filled to a depth of 0.5 feet, for example, the volume is 50 square feet * 0.5 feet = 25 cubic feet.
Divide the volume in cubic feet by 27 to get the volume in cubic yards. For example, 25 cubic feet/27 equals 0.93 cubic yards.
Round up to the nearest 1/2 cubic yard to ensure you get enough material. For dirt, consider ordering another 1 or 2 cubic yards to add on top of the new soil as it settles and compacts.