Calculating how much concrete you'll need for a building or remodeling project not only helps you when setting up a project budget but also saves you time when ordering from a local concrete manufacturing and delivery company or picking up pre-mix from a local home improvement store. It may seem complicated at first, but if you start with accurate length, width and depth measurements and complete a few mathematical calculations, you can order the correct amount of concrete in cubic yards or know how many bags you will need to pick up.
Ordering Concrete Delivery
Measure length and width of your concrete pad or shape in feet. Calculate the surface area by multiplying the length times the width.
Calculate the volume (cubic feet) of your concrete shape by multiplying the surface area by the height or depth in feet. For example, if the surface area you calculated in Step 1 is 1,248 square feet and you are pouring a 4-inch deep pad, you multiply 1,248 by 0.33 (4 inches divided by 12 inches or one foot) for a volume of 416 cubic feet, rounded up.
Calculate the cubic yards required by dividing the cubic feet by 27. In this example, you'll need 15.4 cubic yards, or 16 rounded up.
Pre-mix Concrete Bags
Calculate the surface area of your concrete pad or shape by multiplying the length times the width in feet.
Calculate the volume (cubic feet) of your concrete shape by multiplying the surface area by the height or depth in feet.
Calculate the cubic yards required by dividing the cubic feet by 27.
Multiply the cubic yards by 90 when purchasing 40-lb. bags, 60 for 60-lb. bags or 45 for 90-lb. bags, to determine how many bags of pre-mix are required. For example, if your total cubic yards equal 16 and you are purchasing 90-lb. bags of pre-mix, you will need 720.