Length multiplied by width multiplied by height all divided by 27 is the formula to use to figure out the number of cubic yards of concrete necessary to complete a project. All of the dimensions must be in feet.
When pouring concrete slabs, measure the actual size of the trench, because the dimensions on the blueprints are not always the same as the actual size of the trench. It is always better to order a few extra yards of concrete to account for spillage or over-excavation of trenches. As a rule, contractors should order 4 to 10 percent more concrete than the estimated amount.