how do you want to add the cable? With a background of reverse st st? Or just into the stocking stitch?
If you do not make a "devider" between the stocking stitch (st st) background and the stocking stitch cable they will blend in and be just a little structure.
Mostly either the sweater would be knit in reverse stochinette (just purl on right side and knit on wrong side) or you would make a line of a stitch or two on each side of the cable to devide them from the plain st st. You could also make a background of seedstitch, for example
Just try all 3 methods in your swatch if you do not know what you want. They are all veritable options with different effect. And they will all give a different gauge.
As a standart estimate to start with, I ususally add one stitch to my pattern for every band of cable (if I work on a background of rev. st st). Then you make a swatch and find out, if that works...
Also: the point of the actual crossing of the cables pulls in more than the band itself. So if you make crossings with few rows in between your pullover will be tighter in those spots, than if you left big spaces... just for an estimate.