15x15 is plenty. What all do you intend to put in there? A king size bed is 6'4"x less than 7' for perspective.

Mine is 20 x 16.5". It's a very large space. We wanted a loveseat in front of our bed for various reasons. This was the right size for a king bed + loveseat + tv without feeling cramped.

It definitely depends on what you will put in there and how exactly you want to use the space. If you only want a bed with end tables and a dresser, 15' x 15' would be plenty.

We recently built a 2800 sq ft home in a higher end neighborhood with a spacious master bedroom. It is 17 1/2'x14 1/2' with a king size bed and dresser and still has plenty of space. (I linked a photo so you can get a good feel for the space.) Hope this helps.

Here is a link that might be useful: [Master Bedroom by Dillon Custom Homes[(https://www.houzz.com/photos/round-features-traditional-bedroom-austin-phvw-vp~994255)

It looks as though the bed is on the long wall of the Dillon Homes room with plenty of space between end of bed and dresser.

It really does depend on what all you need in there. If you have lots of doors that cramp the space down, or a weird entrance to the closet, or not enough closet space, ... those will all affect the size/feel of your space.

Thanks for the input folks! We'll have just over 7 feet between windows for the king sleigh bed (huge headboard). Add a dresser, night stands and the old school armoire, and i think we'll be good. At 100 a foot to build, adding 76 feet isn't cheap! Besides, I need the budget for the rainfall shower head!!

Dillon, love the pictures. Thanks for adding those. We'll have french doors to a screen porch where you have those big windows. It really helped.

mine is 13x23 and just big enough for me. but i LOVE my room and we spend a lot of time in it.
we have three walls of windows and the doorway in the center of the fourth wall.
fireplace in west corner, queen bed in east corner ( i love things in corners,lol)
there's a big l-shaped desk in north corner and dressers on south wall.
plus two recliners at the end of the bed with a small bookcase between.
it could be bigger but this is cozy and i have everything i need right here.(laundry, fridge and espresso maker in closet next door).
plus i prefer the proportion of a rectangular room.

Mine is 12x15 (a little snug). I think 15x15 would be perfect for a bed, two nightstands, a dresser, and a bench or chest @ the foot of the bed. If you want more furniture than that in the room, I would go with 20x15.