Answer There is just under half (0.45) of a cubic foot in a 60 pound bag of quikrete.
It takes 133 pounds of quikrete to make 1 cubic foot, so... - there is 0.6 cubic feet (80/133) in one 80 pound bag, and it takes one and two-thirds 80 pound bags of quikrete to make 1 cubic ft (133/80 = 1.66). - there is 0.45 cubic feet (60/133) in one 60 pound bag, and it takes about two and one-quarter 60 pound bags of quikrete to make 1 cubic ft (133/60 = 2.22). - there is 0.3 cubic feet (40/133) in one 40 pound bag, and it takes three and one-third 40 pound bags of quikrete to make 1 cubic ft (133/40 = 3.33).
Multiply by 27 to get cubic yards (so it would take 3,591 pounds or 60 sixty pound bags to make a cubic yard).
To further help calculate how much you need for your project, you can visit: http:/www.quikrete.com/Calculator/Main.asp#concrete