I think that's all the difference is here (from my 6' x 8' 'recommendation'. I now know I shouldn't have said 'finished space'.) Of course, one could cut and cut until they find out that their bathroom IS their closet.
The 'numbers' for bc's and Jim's bathrooms work out just fine. I agree w/them. I guess my perspective was from a dimension that's more tolerable. Don't forget - some day you may want to sell your house. An extra bathroom is nice and so is the 'conservation' of the bedroom, but will it 'sell'? Our communal bath is 5.5' x 8'. (Sounds familiar ...) Merry, if you want to see how big that is, ask a friend or 2 to measure out their bathrooms and have a look-see at a 5.5' x 8' bathroom.
What's it like to lay in a 5' bathtub anyway? I'm 5' 8" and like a bath every once in a while. An extra 12" for a tub, well, THAT'S a great selling point for a 6' x 8' bathroom. (Of course, it's my opinion.)
Aaaaaanyway, like I said, the numbers for bc and Jim work out. Just remember, you have to account for wall thickness (studs, drywall, tile) in your calculations. If you can use pocketdoors for either the closet AND/OR the hallway, you 'gain' some useable space. Happy trails!