Concrete Calculator (Bags + Cubic Yards)

Concrete Calculator

Estimate the concrete you need for a slab, footing or pad — in cubic feet, cubic yards and 40/60/80 lb bags.

Estimate only; add 5-10% for spillage and uneven subgrade. An 80 lb bag of concrete mix yields about 0.6 cu ft. For large pours (over ~1 cubic yard) ready-mix delivery is usually cheaper and easier than bags.
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How much concrete do I need?

Multiply length × width × thickness (in feet) to get cubic feet, then divide by 27 for cubic yards. A 10×10 ft pad at 4 in thick is about 3.3 cu ft × 10 = 33 cu ft (1.23 yd³), roughly 56 × 80 lb bags. Bag yields: 40 lb ≈ 0.30 cu ft, 60 lb ≈ 0.45, 80 lb ≈ 0.60.