Quick answer
Use concrete bags for small repairs, fence posts, and very small slabs. Use ready-mix for larger pours because it is faster, more consistent, and usually easier once the project needs about one cubic yard or more.
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Best for bags
Small repairs, post holes, steps, and projects under about 1 cubic yard.
Best for ready-mix
Patios, driveways, large slabs, footings, and projects where consistent strength matters.
Main tradeoff
Bags are flexible but labor-heavy; ready-mix has delivery minimums but saves time.
Common questions
How many 80 lb bags make a cubic yard?
About 45 bags of 80 lb concrete make one cubic yard.
When does ready-mix make sense?
Ready-mix usually makes sense when the job approaches one cubic yard or when labor speed matters.