I expect to be asking several more questions about this project; but I'm starting with a general one, and will get more refined as things develop.
We are working on finishing our basement, which includes a bathroom. In the original plans, the bathroom was 5' x 8'; which is very tiny. This matches the size and planned layout of a bathroom upstairs, so we've an idea how cramped it will be. We would like to enlarge it a bit, and move some things around to make it more... usable.
The uncertainty I'm running into is dimensions. For example, toilets are typically about 22-24" wide; but most people would be more comfortable with some clearance on either side. I'm uncertain how to estimate the space needed for a toilet. Similarly, counters are usually 24-30" deep; but putting in a sink typically defines a minimum cabinet depth. Finally, while the original plans called for a tub/shower (side entry), we're planning to change that to a corner shower. Tubs seem to be 30" wide; but I expect a corner shower to be wider (perhaps 36" x 36"). And if the shower has a corner entry, should I allow more space to enter/leave the shower?