Estimate concrete volume, cubic yards, cubic feet, and bag counts for concrete slabs, patios, shed pads, garage pads, and other flat slab projects.
Slab volume formula:
Length × width × thickness = total slab volume
Conversion formula:
Cubic feet ÷ 27 = cubic yards
This calculator estimates slab concrete volume, cubic yards, and approximate bag count with extra material added.
Knowing how much concrete your slab needs helps when planning patios, shed pads, garage pads, walkways, and other flat pours, while reducing the risk of coming up short.
Extra material is often useful for grading differences, edge loss, and form inconsistencies.
Your result shows the estimated amount of concrete needed for a flat slab based on the dimensions entered. The total includes an optional extra percentage to help cover waste or slight overages.
The estimate also includes an approximate bag count based on the bag size selected. For larger slab pours, ready-mix ordered by cubic yard is often easier than mixing bags.
Multiply slab length by slab width by slab thickness to get the total volume, then convert it into cubic feet, cubic yards, or cubic meters.
One cubic yard equals 27 cubic feet.
Yes for many projects. Extra concrete helps cover spills, over-excavation, uneven thickness, and form variations.
Yes. This calculator provides an approximate bag count based on common 40 lb, 50 lb, 60 lb, and 80 lb concrete bag yields.