Calculate the volume of concrete needed for a slab, footing, or wall, along with an estimated number of concrete bags.
This tool estimates how much concrete you need for a project by calculating volume from the dimensions of a slab, footing, or column, then converting that volume into the number of concrete bags or cubic yards/meters required. It helps avoid ordering too little (causing project delays) or too much (wasting money).
Volume = Length × Width × Depth (or Thickness). For circular columns, Volume = π × r² × height. The result is typically converted to cubic yards or cubic meters for ready-mix ordering, or divided by bag yield (commonly 0.45 or 0.6 cubic feet per 60–80 lb bag) for bagged concrete.
Enter the length, width, and depth of your slab or footing (in the same unit), and the calculator returns the total volume needed, along with an estimated number of bags if applicable.
Example: A slab 10 feet long, 10 feet wide, and 4 inches (0.33 ft) thick needs 10 × 10 × 0.33 ≈ 33 cubic feet of concrete, which is about 1.22 cubic yards.
Should I order extra concrete? Yes, most contractors add 5-10% extra to account for spillage, uneven subgrade, and measurement variance.
What's the difference between cubic yards and cubic feet? One cubic yard equals 27 cubic feet — ready-mix concrete trucks are typically ordered in cubic yards, while bagged concrete is usually calculated in cubic feet.
How thick should my slab be? Standard residential slabs (patios, sidewalks) are typically 4 inches thick, while driveways for vehicles often need 5-6 inches for added load strength.
Does this account for rebar or wire mesh volume? No, this calculates raw concrete volume only; reinforcement materials are calculated and ordered separately.
How many bags of concrete do I need per cubic yard? Roughly 45 bags of 60 lb concrete mix, or about 60 bags of 40 lb mix, are needed to make one cubic yard.