Increasing stitches to make a cardigan

[CraftyHooker]

Hello! I am hoping to get some advice on how to appropriately increase my stitches when making a top/cardigan. For example, I am a size M/L and if I was making a simple cardigan using dc, what exact formula is there to figure out how many stitches per row to increase?

[magiccrochetfan]

There is not a single formula for increasing.  If you make a really simple cardigan, the pieces will be rectangles and you don't have to increase at all, just make straight-sided pieces.  

 

If you do shaping for bust/waist/hip, shaped neckline, and a tapered sleeve, you will need to increase and/or decrease at different points, but there still is not a single formula for this, because it depends on the measurements you are working to, and your stitch and row gauge with the chosen yarn and hook.