Concrete Calculator (Slabs, Footings & Bags)
Calculate required concrete volume in cubic yards (yd³), cubic meters (m³), and determine exact 60-lb and 80-lb pre-mixed bags needed for slabs, driveways, and footings.
Slab Dimensions
Standard practice is to add 10% for uneven subgrades, subbase settling, and formwork deflection.
Standard unit ordered for ready-mix concrete delivery trucks.
Pre-mixed Concrete Bags Needed (Quikrete / Sakrete)
How it works
1
Select project geometry: rectangular slab/driveway or cylindrical column/post hole.
2
Input length, width, and slab thickness (standard 4 inches) in feet and inches.
3
Review required cubic yards, cubic meters, and pre-mixed bag tallies with a 10% safety buffer.
Frequently asked questions
How many 80-lb bags of concrete make a cubic yard?
It takes 45 bags of 80-lb concrete to equal one cubic yard (27 cubic feet), since each 80-lb bag yields 0.60 cubic feet.
When is it cheaper to order a concrete truck instead of bags?
Generally, if your project requires more than 2 cubic yards (equivalent to 90 eighty-pound bags), ordering ready-mix delivery by truck is both cheaper and significantly less labor-intensive.
Is this tool free?
Yes. The site is supported by ads, so you never pay or need to create an account.
Does it work on mobile?
Yes. The page adapts to your screen and does not require installing any app.