Thank you for all the adive. What happened when I did the foundation I wasnt thinking abotu the studs and drywall therefore I short changed myself abit and I didnt at the time think I was going to add a toilet. Major mistake on my part. I only envisioned a bathroom when I started laying the subfloor.
So my box is 12x24 and I also want to have a place to do framing and mat cutting in the front of the darkroom wall. The 3x5 bathroom really takes up more space than I planned. I was hoping to get away with 8x12 but it seems that it will not work to good.