Typical 80 lb bag ≈ 0.60–0.67 ft³—read your product sheet.
Needed volume in cubic feet and each bag's yield in ft³ (check bag label)—bags to buy (rounded up).
Typical 80 lb bag ≈ 0.60–0.67 ft³—read your product sheet.
With total concrete volume (ft³) and yield per bag (ft³ per bag) (both positive), the page uses bags = ⌈volume ÷ yield⌉. The second line restates the inputs as a quick sanity check; slump, waste, and partial bags are not modeled beyond rounding up.
This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.