To calculate how much hardscaping material you need, first measure the length and width of the area you want to cover. Multiply the length by the width to get the total square footage. Then, determine the thickness of the material you plan to use, and convert that measurement to inches (if necessary). Multiply the total square footage by the thickness (in inches) to get the total cubic footage. Finally, divide the total cubic footage by the number of cubic feet in each bag or pallet of the material to determine how many bags or pallets you will need.