The exact size of a 55-inch TV depends on a number of things, but a standard wide format screen is 26.96 inches tall and 47.94 inches wide. A traditional format screen with a diagonal of 55 inches is 33 inches tall and 44 inches wide.
With the traditional 4:3 aspect ratio, the height and width of any size screen can be found by multiplying the diagonal size by 0.6 for the height and 0.8 for the width. With a 16:9 aspect ratio, you can find the height and width of a widescreen by multiplying the diagonal size by 0.49 for the height and 0.87 for the width. The actual size of the TV depends on a number of things, like the size of the case and the bezel that goes around the screen.