I would recommend you a TV screen size more on the basis of where you sit, rather than the room size. Because it is not possible that you would view the TV, allowing the entire room size to be left in between. So, here is a simple way to calculate that. Here are the steps to follow:
1. Measure up the distance right from the end of your seat till the edge of the TV in inches and then multiply by .84. That will automatically give you the screen size that is going to be ideal for you. To be more accurate and get some help with the calculation, you can feed in the measurements in the following place and get your screen size automatically calculated.
2.To be on the easier side, in most living rooms of a standard size, a 50-inch TV is good enough for easy viewing provided you keep a minimum distance of four feet from the TV.
3. The wall-size matters too in this respect. In your case, if you are done with deciding on which wall you have dedicated for the TV, the size would get somewhat decided there itself, as it certainly cannot exceed that.
4. The Price or to be specific, your budget is yet another deciding factor behind the purchase. As you know the price would vary as you increase in screen size. So, you can go as bigger with the screen size, as your pocket permits.
5. The last thing to be noted is the angle. It should not be that big, that your neck has to adjust itself too hard. It should go easy with your sitting gestures, especially if there are kids at home. The final thing to ponder over is that the look of the room should not get suffocated with the TV screen size and you should leave at least a foot distance at the edges of the wall so that it gives an eye relief when you watch it.