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How to estimate concrete for your project
Concrete is estimated by volume: multiply your slab area by its thickness to get cubic feet, then convert to cubic yards or bags. This calculator shows both, plus the number of 80 pound and 60 pound bags, since bagged mix is how most small pours get done.
An 80 pound bag of concrete mix yields about 0.6 cubic feet, and a 60 pound bag about 0.45. For anything past roughly a cubic yard (around 45 to 60 bags), a ready-mix truck usually beats mixing bags by hand.
Frequently asked questions
How many 80 lb bags of concrete are in a yard?
An 80 pound bag yields about 0.6 cubic feet, and a cubic yard is 27 cubic feet, so it takes roughly 45 bags to make one yard. With 60 pound bags (0.45 cu ft each) it is about 60 bags.
How thick should a concrete slab be?
A 4 inch slab is standard for patios, walkways, and shed floors. Go to 5 or 6 inches for driveways or anything that carries vehicle weight. Enter your thickness above and the calculator handles the volume.
When should I order ready-mix instead of bags?
Bagged mix is fine up to about a cubic yard. Beyond that, mixing 45-plus bags by hand is slow and inconsistent, so a ready-mix delivery is usually cheaper and gives a stronger, uniform pour.
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