Slabs, footings and columns — in cubic yards, bags and cost.
80 cubic feet, which is 2.96 cubic yards. With 10% waste you would order 3.25 yards, since ready-mix comes in quarter-yard steps.
45. An 80 lb bag yields about 0.6 cubic feet and a cubic yard is 27 cubic feet. A 60 lb bag yields 0.45 cubic feet, so 60 of those.
About 4,050 lb, just over 2 US tons, at the standard 150 lb per cubic foot.
Multiply length × width × thickness in feet, then divide by 27. A 20 × 12 ft pad at 4 inches is 80 cubic feet, which is 2.96 cubic yards of concrete.
No, this is concrete volume only. Work out a compacted gravel base with the gravel calculator; reinforcement comes from the slab design.
Multiply length × width × thickness in feet, then divide by 27 for cubic yards. Thickness decides the cost: four inches suits patios, walkways and sheds, five to six inches where a vehicle parks, and going from 4 in to 6 in adds 50% to the concrete.
The same figure goes by several names on a job: concrete yardage, cubic yards, or simply "the yards". A concrete pad, patio slab and shed base are all calculated the same way — area × thickness ÷ 27 — and the weight column tells you what the finished pour will put on the ground.
A cubic yard is 45 eighty-pound bags. Most people switch to ready-mix at about that point, because a slab has to be poured continuously to avoid cold joints.