Figuring your needed amount of concrete for a project is the easy part. Forming, pouring, and finishing the concrete is the hard part. Most slabs are poured at 4 inches thick. You take the length of the formed area and multiply that by the width. Take that total and multiply it by 0.33 for a 4 inch thick slab then divide that total by 27 for the total yards of concrete you will need to pour the slab. Here is an example calculation for a 10 X 12 slab at 4 inches thick.
10 x 12 = 120 x 0.33 = 39.6 divided by 27 = 1.46 yards of concrete.
W x L x 0.33 / 27 = Total yards of concrete needed at 4 inches thick.
W x L x 0.49 / 27 = Total yards of concrete needed at 6 inches thick.
W x L x 0.66 / 27 = Total yards of concrete needed at 8 inches thick.
*Note- It is always a good idea to add just a little to the total amount of concrete that you figure simply because it is better to have a little extra than to come up short.
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