Concrete Slab & Post Hole Calculator
Calculate concrete volume in cubic yards, cubic meters, and exact bag counts (80 lb, 60 lb, 50 lb) for slabs, driveways, footings, and fence post holes with spillage margins.
Project Dimensions
Estimated Order Quantities
Concrete Volume Calculation & Ready-Mix Sizing
In residential and commercial masonry, concrete is ordered in cubic yards (1 cubic yard = 27 cubic feet = 0.765 cubic meters). Ordering accurate volume prevents cold joints, where fresh wet mix fails to bond with partially cured concrete.
Slab Volume Formula
(Length [ft] × Width [ft] × Depth [in] / 12) ÷ 27 yields total cubic yards. Adding a 10% waste buffer accounts for irregular subgrades and form deflection.
Bags vs Delivery Truck
One 80-pound bag yields 0.60 cubic feet (45 bags per cubic yard). When a project requires more than 1.5 cubic yards (68 bags), ordering ready-mix delivery avoids extensive manual mixing labor.
Footing Depth Guidelines
Cylindrical pier footings and fence post holes must extend below local frost depths (often 30 to 48 inches) to eliminate structural heave during seasonal freeze-thaw cycles.
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