Answer:
The average tube of caulk covers 30 lineal feet when applied at a quarter inch bead. Check on the tube of caulk you want to use; there should be coverage details on the tube with all the other information. Measure or guess how many feet are in need of caulking, and how much over or under a quarter inch bead your going to be, and how deep your filling; if it is over a half inch use backer rod. It takes a lot of guesswork.