The general rule of thumb to keep in mind is not to try to feed your beardie anything larger than the space between its eyes. If you do, there's a chance your bearded dragon could choke on it.
Also, from what I've heard, pinkies are pretty high in fat, and should be an occasional treat (one or two per month if that).
If the length OR width of the mouse is bigger than the space between your dragon's eyes, he definitely shouldn't eat it. Go by the largest "dimension" of the mouse. If it's as wide as his eyes but longer than his head, go by the length, which in this case is much bigger than the space between your dragon's eyes.
I am going to throw in my two sense there is absolutely no reason to feed your beardie pinkies. I have no issue feeding mice to other reptiles. Make sure if you choose to it is a pinky all the hair and bones on a mouse would be a big impaction risk.