Concrete Calculator
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Concrete, without the guesswork
Pick your shape (slab, footing, column, wall), enter dimensions, and get cubic yards, bag count, weight and cost — with adjustable waste % and 80/60/50 lb bag sizes. The gap calculator.net leaves (no bags, no cost, no waste) is filled.
Frequently asked questions
How many 80 lb bags in a cubic yard?
About 45. We use the industry standard (0.022 yd³ per 80 lb bag) and round up — you can't buy half a bag.
Why add waste %?
Spills, over-excavation, uneven subgrade. 10% is standard; use 5% for precise forms, 15%+ for rough ground.
How thick should my slab be?
4" for patios/walkways, 6" for driveways (car traffic). Thicker isn't stronger without rebar — it just costs more.
When should I order ready-mix instead of bags?
Over ~1 cubic yard (45+ bags), ready-mix trucks are cheaper and far less labor. Our cost estimate helps you compare.