A little more information about the space you have would help us help you
better. There are many ways this can be arranged.
This is the question. We have a small sleep room about 10 x 13''. We want to
extend it by additional 3-4'' on one wall. I'd like to add a small bathroom
to the room without sacrificing the room space. So the question is how small
can a bathroom and still remain comfortable. I remember in japanese hotels I
wondered how small the bathroom were, and even they had a bathtub. So the
size of the projected bathroom can be increased at expense of the sleep room
but I think it is better to have a bigger room...

Thanks for the answers. I'm still looking for the appropriate size...
Sammy