Estimate exactly how much concrete you need. Works for slabs, footings, and foundations. Get cubic yards or bag counts.
Concrete is ordered by the cubic yard (27 cubic feet = 1 cubic yard). The formula is simple: Length × Width × Depth (in feet) ÷ 27 = Cubic Yards.
Example: A 10×10 ft slab at 4 inches deep = 10×10×0.33 ÷ 27 = 1.23 cubic yards. Always order 10% extra.
Ready-mixed concrete: Ordered by the cubic yard, delivered by truck. Best for projects over 1 cubic yard (54+ 80lb bags).
Bagged concrete: Sold at hardware stores. One 80lb bag yields ~0.6 cubic feet. Only practical for very small projects (<0.5 cubic yards).
A 10×10 ft slab at 4″ thick needs 1.23 cubic yards of concrete. Add 10% extra = 1.35 cu yd. Order 1.5 cu yd to be safe.
Multiply length × width × thickness (in feet), then divide by 27 to get cubic yards. Our calculator does this instantly and adds waste margin.
Order ready-mix for projects over 1 cubic yard (≈ 60 bags). For small jobs (steps, piers), 80lb bags are easier. 1 bag = 0.6 cubic feet.
Walkways: 4″. Patios: 4-5″. Driveways: 6-8″. Garage floors: 4-6″. Thicker slabs need more gravel base and rebar.
Ready-mix concrete costs $125-150 per cubic yard (delivered). Short loads (< 5 yd) add $50-100 extra. Bagged concrete: $5-7 per 80lb bag.