How Many Stitches

Alrighty, I have an issue lol What or I shuld say how do I know how many stitches to make when knitting a slipper? I mean I’m making slippers for my mom and she has size 6 US womens feet. But I have no idea how to figure out how many stitches I need to cast on. Any suggestions?
:thinking: [/b]

what kind of slippers are you making?

Are you following a pattern? It might be easier if you are new. Here’s a bunch.