Almost everything can be made smaller. Boats, trains and airplanes have bathrooms. Hand rinsing sinks can be as small as you can imagine. The tap can come from the ceiling or wall over the sink. ETc.

Showers can't be made infinitely smaller because your body size (and elbows) have dimensions that are not elastic.

If you have little money, you go web searching and find the cheapest shower made of something plastic. Or you just go to a big box hardware store in a low rent area and pick up whatever they have.

If you have a lot of money, you get something custom built and it looks beautiful because spending a lot of time and money in a small area makes it end up looking like an investment, and the fact that it is so small means you end up with aesthetic choices that don't all clash with one another. It's so small that you won't be adding curlicues and changing tile patterns often, and so on. For one kind of layout option, search using these three key words: "wet room" bathroom .

hth

Code restrictions will dictate some of your minimum dimensions.

Minimum shower size by code is 30" by 30", interior dimensions.

There are restrictions for sink, the toilet, etc. The toilet requires 15" on either side of the toilet centerline (thus minimum 30" wide space) and 24" minimum in front of the toilet.

So your space is too small for a traditional walled in shower.

The way to eliminate may of these and get a truly compact bath is to make the entire bathroom a wet room which would allow you to eliminate shower wall partitions. Think of the entire bathroom as an an over-sized shower with a toilet and a sink. You could have the sink and the toilet wall mounted to get them off the floor. Oh, there are corner sinks and corner toilets too.

Thank you both for the thoughts. I never had heard of a wet bathroom. Googled it and looks very interesting. Am going to read some more.

Code issues aside, you can do this. My uncle did this in his NYC apt and I kid you not, this bathroom with toilet sink and shower is not more than 30" wide. Incredible, I know. The toilet is alone on one end of the bathroom (all the way to the end. The entire bathroom has a tiled floor and the walls and ceiling are tiled in the shower end of the room. He actually has two shower heads (one in the ceiling and one comin off the wall) and the floor slopes toward the drain. He has a very tiny sink on one wall. I can tell you it's one of the greatest showers I've ever been in. Door placement is key to this setup. Obviously the door has to be as near to the toilet as possible. There is almost no room for shampoos and towels but who cares. There is also no curtain of any kind, although I suppose you probably could put one up. It can be done!

LOL - regarding "wet rooms": have you ever seen a European bathroom not in a first class hotel? They seem to have missed the whole shower door/shower curtain thing altogether. It makes for an interesting showering space. If you do this, I'm sure you'll plan ahead and make sure all the walls and floors are waterproofed.

Maybe you could add a third bathroom in a vacant broom closet! Just kidding. Just a stool and very small vanity. And maybe a pocket door.

The space is actually any unfinished closet area. It is above where the stairs come up so the main area is 41 by 55 on the flat and the stairway slant goes several feet more up.
I wouldn't need to worry about any code. This is an old farmhouse.