Really it depends on how large the snake is.

I go by this feeding rule: feed your snake a mouse/rat about the same size as the middle part of the snake's body.

Here's an example of that rule: The middle part of my female BP is about the same size as a small f/t rat. Now, I feed her small f/t rats. These past two weeks went great, and now she's shedding because I've been feeding her those rats.