Do you mean size of the space to work with? The shower looks to be about 4x4 and the tub space looks to be 72". Those tiles are 6"x12". So overall that space is likely 10'x4' give or take 6". The drain systems could be tied into one another as it is likely you would not be using both at the same time.

A few other changes to this layout, change the location of the tub spout, if 2 people are in this tub the spout is in the way, and add a hand shower to the shower. Otherwise, gorgeous and I do this combo quite frequently!

If the tiles are 12" then this is 11.5 '. What is the minimum size a stand up shower should be? I only have 10'4" and this is the design I want.

Could you let me know the name of the light gray tiles and the supplier. Thanks.

Tile looks like carrera marble.

The minimum size a shower should be is 3' x 3'. At that size it does feel slightly cramped so if you could make it 3' x 4' it would help considerably. Another idea, if you don't actually use your tub or if you are average height you could consider going to a shorter model 60" or 64" to give you more shower space. I'm not sure your total area but you could also consider a wet room.

Hope that helps.

Could you please share the grout color? I think its perfect with the carrera

i would say they should definitely be able to share the same 2 in. drain. besides, chances are pretty good that the tub and shower wouldn't be draining at the same time very often.