on a 1920x1080 display using bitmap fonts or their equivalent where each cell is 8x16, then three tiled windows without borders are 80 characters wide. font used is unifont, i3 window manger, xst terminal, vim, etc.
if i had a 2560x1440 display, i'd use four 80 character wide tiled windows.
if i had a 2560x1440 display, i'd use four 80 character wide tiled windows.