How many pixels in a unit in Unity3d?

Question

I know this question has been asked multiple times before, but how many pixels is one unit in Unity? The answer seems to be that it is whatever you want it to be (the typical answer is that it is relative, 1m and has something to do with the physics).

But it has to translate to pixels somehow in the context of sprites? Take for instance this 64x64 pixel box:

Answer 1

You can see how many pixles it is per unit. Unity has 100 pixels per unit from the start (at least for me) and you can change it for each sprite. If you select a sprite (in the project tab) it should look something like the image below and from there you can change it to whatever you want.