Mounting your TV at the corner of the room it always presents some challenges. The first challenge is to find the right full motion TV mount with right arm extension and the second is to position the wall plate of the TV mount at the right distance from the corner of the wall so your TV will fit perfectly in the corner.
As you can see from the picture above this is a full-motion TV mount with 2 arms that can be extended 19.7 in. On the right side of the TV mount there is the wall plate that is attached on the wall and the left side is where the TV mount is attached to the TV. The Wall plate of the TV Mount should be at least 24in in length so it can be attached to 2 wall studs.
Above there is the diagram of the corner of the wall, the TV length that fits in the corner, the arm extension of the full motion TV mount(BD) and point (B) is the position where the middle of the wall plate of the TV mount should be located so the TV will fit exactly catty-corner.
In order to determine the arm extension that your full motion tv mount must have, first you have to measure your TV length. The TV length is not the same as the size of the TV because the TV size is measured diagonally and not horizontally. Once you determine the length of your TV then you can find out how long the TV mount arm must be from the following formula: Minimum TV Mount arm Length(BD)=0.5*(Length of TV/1.41)
It also happens that the middle of the tv mount wall plate must be position at the same distance from the corner of the wall (A) as the length of the arm of the full motion tv mount because the distance of (BD) equals the distance of (AB).
So lets take an example. The size of my TV is 55in but the length (including the bevel) is 51in. What is the min arm length full motion TV mount I should purchase so my TV fits perfectly in catty corner of the room? and where I should place the middle of the wall plate from the corner of the wall?
And the answer is: 0.5*(51/1.41)=18 inches…. The full motion mount in the pic above will do the job.