Patios are an investment that you put into a property. You want the patio to look nice and be stable during weather changes. Before you order concrete, which is a mixture of water, sand, aggregate and cement, you need to know how much concrete is needed. For patios, the concrete should be 3 1/2-to-4 1/2 inches thick to prevent cracking. Using any more than 4 1/2 inches would be a waste of money for a backyard patio.
Use the tape measure to measure the length of the area for the intended patio in feet.
Measure the width of the patio in feet.
Multiply the length by the width, both in feet, by the thickness in inches and divide it by 12 to get the cubic feet you would need. For instance, if the patio length is 5 feet, the width is 6 feet and the thickness is 4 inches, your calculation would be: 5 times 6 times 4 divided by 12, which would equal 10.
Divide the total cubic feet by 27, since there are 27 cubic feet to a yard. In this instance it would be 10 divided by 27 would equal 0.37 cubic yards.
Purchase 0.37 cubic yards of concrete from a supplier. If you are mixing the concrete yourself, you would need 34 40-lb. bags of pre-mix concrete, 23 60-lb. bags of concrete or 17 80-lb. bags of concrete.