I've never measured it.
I know it varies. If I'm not fully aroused, and we're playing with toys, the dildo barely gets in and can just fall right out. If I'm fully aroused, we can get a fairly large one in almost to the controls or the end. My husband's a pretty big boy and I am used to his size for years, so I wonder if my body just adjusted to that when I was younger and is used to increasing length and width for whatever is available.
Vaginal depth and width are not static. Arousal, where you are in your cycle, and other things all have effects on both.
As I've said before, vaginas are made of Memory Foam!