Concrete Calculator
Work out concrete volume for any slab: length, width and depth in feet, converted to cubic yards and 80 lb bags.
About this tool
Enter slab length, width and depth in feet and inches: this calculator gives the volume in cubic feet and cubic yards plus the count of 80 lb bags for DIY pours, with waste included.
The difference between ordering one extra yard and running short mid-pour is a weak cold joint. This takes the guesswork out — and tells you when a ready-mix truck beats carrying 40 bags.
FAQ
How many yards of concrete do I need?
Length x width x depth in feet, divided by 27. A 10x8 ft slab 4 in deep is 2.47 cubic yards.
How many bags make a yard?
About 45-50 bags of 80 lb per cubic yard with water and mix allowance — bagging is practical only under about 1.5 yards.
What happens if I run short?
Cold joints form where pours meet. Always order 5-10% extra; leftover can be used for stepping stones.