Tile size 80x80 in the bathroom

Is there a - let’s say - recommendation on which tile size should be used for a guest WC with a width of 1.38m and a depth/length of 2.26m including a pre-wall installation of approx. 20cm on the rear wall? So that you would have a good 2m of tiled floor.

Or which laying direction would be optimal?

Thanks!

For this size, I assume there is no shower and a wall-hung toilet, so the floor space would not be affected by objects. Without knowing the window side, your second question cannot be answered. What do you tend to prefer? - for large and square, I could well imagine 80/80 (and because of 138 = 2n + cutting loss better than 60/60), but also 60/30 under the condition "laid along the room axis," because then 138 = 4n + a proportionally pleasantly sized remainder.

Yes, exactly. No shower and a wall-mounted toilet.

If you placed 80s side by side, it might look a bit strange because the toilet bowl is not centered. Thus, the bowl would not be aligned with the middle joint... which would be the case if mounted centrally.

Mentally, I would go for a half bond. I would exclude a quarter bond because the slightly offset joint from the other would always cause me to think "that's crooked".

What kind of floor is running outside against it (transition at the door)? If there is a different floor there, maybe parquet etc., then I could also very well imagine the floor made of a tile. Not a plain tile but one with texture. (You might notice from my answers that I am a fan of large tiles)

Outside, so in front of the door is the hallway. It will also get tiles.

Now came up with the idea of working with an "extra-wide" tile. The guest WC is quite narrow at 1.38m. Place a tile in the format 150x75 across the width, so shorten the 150 side lengthwise. (The rest could even be used as a baseboard). And thus lay 3 rows from back to front. Few joints and also because the WC is somewhat off-center, there are no disturbing longitudinal joints from the view.

Thinking error? Would that be a measure?

That would of course work. Whether it looks good naturally depends on the tiles (format) that are laid in the hallway. If, for example, 60x60 tiles are laid there, I would use the same format for the guest WC. Do you want to lay tiles yourself? If yes, you have to consider with the large tiles that most cutting devices only go up to 60cm. Of course, there are larger ones, but the ones you usually have at home are mostly only up to 60cm.