Method
How to calculate concrete required in cubic yards
Depth is converted from inches to feet. The resulting cubic feet are divided by 27 to obtain cubic yards.
FORMULACubic yards = length × width × depth in feet ÷ 27 × waste factor
Worked example
Concrete calculator example
A 20 × 12 ft slab at 4 inches deep contains about 2.96 cubic yards before waste.
Change one assumption at a time to see what drives the result. The output is an estimate, not a quote, forecast or recommendation.
FAQ
Concrete calculator FAQ
Why include a waste allowance?
Spillage, uneven subgrade and ordering increments can make delivered volume exceed geometric volume.
Can this calculate footings?
Yes for rectangular footings; calculate each distinct shape and add the volumes.
Does this specify concrete mix?
No. Strength, reinforcement and mix design require project-specific engineering guidance.