Distance from Seating to Screen size

There are some calculations made such as this one for THX
http://www.thx.com/consumer/home-entertainment/home-theater/hdtv-set-up/ .

But some prefer different, I sit roughly 7ft from my 100" diag screen which is close to even THX calculations. But some choose to sit further away.

Screen width X 1.5 = seating distance. EX: 8' wide screen(110") X 1.5 = 12' seating distance.

There are guidelines, but ultimately it comes down to preference - hang a sheet for a temporary screen, and project onto it to decide what size you like, before ordering your screen.

I'm 12' from a 136" wide 2.125:1 aspect ratio screen, so I'm on the "I like immersive" end of the spectrum.

That will be fine. The old rule was twice screen width, then we got HD and it came down to 1.5 screen width. I sit at almost 3 times screen width, and while it isn't as immersive, I think how much better the 80" wide screen is than a 40" LCD would be (I can only fit an 80" screen by using a pull-up model , and a 40" would be the max permanent TV I would be able to put in the living room without blocking dining room entry.)

I love this site: Plug in the distance you are away from the screen and it will give you min and recommended screen size. This is based on a theater experience! This has been very helpful. If you are only 10 feet away from the screen like my room....you don't want a 120 inch screen...it would be ridiculous like sitting in the front row of a movie theater. For my room it said it recommended an 89" diagonal (Min 73") and I'm at 84"! It looks great in my room!

http://myhometheater.homestead.com/viewingdistancecalculator.html

If that's the biggest you can go...it's a no brainer. I would try to arrange my seating closer. Using the site I posted they reccomend no further away that 13.9 feet away for a true theatre xperience. I'm sure it will be fine!! But arrangements of seating could help!!

One additional data point - if you get a screen that's too big, you can move seating back, or adjust zoom and mask it down; if you get a screen that's too small, you can move seating closer, or buy a new screen.