Ordering concrete short means a cold joint and a callback; ordering too much wastes money on every truck. This calculator converts slab, footing, and column dimensions into cubic yards, adds a waste factor for real-world pour conditions, and converts the result into exact 60lb or 80lb bag counts when a job is too small for a ready-mix truck.
24 ft × 24 ft × 4 in thick, 10% waste.
4 footings: 10×1×12 in each.
50 ft × 4 ft × 4 in thick, 10% waste, ready-mix at $165/yd³.
A standard ready-mix truck holds 9–11 cubic yards. Minimum loads are typically 1 yard (short-load fees may apply under 3–5 yards depending on the supplier). For small jobs under 2 yards, bagged concrete is usually more practical.
An 80-lb bag yields approximately 0.60 cubic feet. One cubic yard = 27 cubic feet, so you need about 45 bags per cubic yard. A 60-lb bag yields 0.45 cubic feet — roughly 60 bags per yard.
Standard residential slabs (patios, garage floors, sidewalks): 4 inches. Driveways with light vehicle traffic: 4–6 inches. Heavy truck traffic or commercial: 6–8 inches. Footings are typically 12 inches deep or per local code. Always check local building codes for your specific application.
Concrete volume calculations assume perfectly flat, square forms. In reality, subgrade variations, form deflection, and spills add 5–10% to actual usage. Ordering 10% extra is standard — running short means a cold joint, which is a structural defect.
A slab is a flat horizontal surface (floor, patio, driveway). A footing is a below-grade structural element that transfers building loads to undisturbed soil. Footings are typically narrower and deeper. Both are calculated the same way (length × width × depth) but footings often have depth measured in inches or feet below grade.