4' x 6' is plenty big. 42" by 66" is good, 60" is the minimum length I'd recommend for a typical 2-person shower. I try to not go narrower than a 42" width, with "width" being elbow-to-elbow.

Your shower head locations are fine on the end walls. If you can put the supply valves by the door, you can turn on the water without having to step in the shower.

If you're having a hinged door, I'm guessing (oops) that it'll be hinged on the 16" partition wall? If so, then consider having the two supply valves on the 25" partition wall. They can be stacked.

My own shower is 5' by 8', no door. Plenty warm without a door, no splash out when showering, and plenty big for two.

My DH and I have had 2 different 2 person showers. The first was 5x5 with the shower heads on the same wall. the opening was about 24 inches wide and was on the side wall. Our second shower is 5 wide x 4 deep & has the shower heads on a 5 foot wide wall. The opening is in the corner next to one of the shower heads. This is plenty big enough for us. We do not have a door we use a shower curtain. Hope this helps.

Our 2-person shower (previous home) was about 42"+ by 5-1/2' (with a bench on one of the short ends -- never used, waste of space for us). The door was where your picture says "25". One shower head was on the wall that's lowest in your picture and the other shower head was on the long wall next to the door. Worked for us and we showered concurrently most weekdays.

As sjhockeyfan said - we had a bench in our first shower, the 5 x 5 shower - and used it very rarely. No bench in this shower. If needed we could easily get a shower bench.

Thanks for the responses. Interesting comments about the bench.

Do you think these showerheads are in the best place? My first priority is that it works well for 2 people showering at once, but it would be a nice "bonus" if only one person is in there and you could turn on both showerheads at the same time for front-and-back spray (I'm guessing it would be rarely used because of water considerations, but nice to have it available!). Is 6' too far away for this?

I'd also like to avoid spraying at the door opening as much as possible, so I would think the showerhead at the top would be in a fine spot but I've thought that the one on the bottom might have a wide spray and hit the door? Would it be better to put the showerheads on the top-right and bottom-right corners and have them spray towards the middle of the left wall on the diagram? That seems like it may avoid spraying the door as much, but would it be as comfortable to use?

Here's a picture of this possible layout:

Here's a 3rd layout, I think it is what sjhockeyfan325 was saying if I'm understanding that correctly. Any thoughts?

We are going with a 4'x4' shower & consider it a 2 person shower. We have fit 2 adults & a child in our current 3x3, so the extra space will be awesome!! Will you have a bench?

What would be the minimum width if both shower heads were on the same wall?

To echo some previous posters I had a tiled bench in my large shower and found it cold to sit on despite the warm water- never used it and considered it a waste of space. I have not had one since but if I wanted one woul either get a fold out from the wall teak one (warmer) or just use a portable one

I want to say… as a female we likes my legs clean shaven I love the bench to place my foot on when I shave so I must have one to make my shaving ritual easier. Just a female input

amen for the shaved legs. You need something to put your feet on!