Concrete guide
Concrete calculator: yards and bags for a slab
Convert slab length, width, and thickness into cubic feet and cubic yards, then estimate ready-mix bags with a 10% planning overage.
Choose a bag size and enter your slab dimensions for an instant quantity estimate.
Use the concrete calculatorHow the concrete estimate works
Thickness is converted from inches to feet, then multiplied by slab length and width. Cubic feet are divided by 27 to produce cubic yards. For bags, ProjectReady divides volume by the approximate yield of the selected bag and adds 10% before rounding up.
Cubic yards = length (ft) × width (ft) × (thickness in ÷ 12) ÷ 27
Approximate bag yields used
- 40 lb bag: 0.30 cubic feet
- 50 lb bag: 0.375 cubic feet
- 60 lb bag: 0.45 cubic feet
- 80 lb bag: 0.60 cubic feet
Actual yield varies by product, so confirm it on the bag before purchasing.
Plan the pour carefully
Ground conditions, forms, reinforcement, drainage, slab thickness, and local building requirements affect a project. This calculator estimates material volume only; it does not determine structural design.