What are the exact dimensions of the Brew Bucket?

20.6" height x 12.5" width.

Note that height does NOT include stopper, bubbler, and blow off setup you have, etc. This is only to the top surface of the lid.  

Add a few inches depending on what you use up there and of course using a blow off tube or a 90-degree elbow tube coming out of your stopper can save some height as well if you are fermenting in a tight space.