Choosing a screen size for a flat-screen TV is a factor of room size, particularly the distance from the audience to the TV itself. If you sit too close to the TV, you are more likely to notice small imperfections in the image or even pixels. Sit too far away, and you lose the impact of owning a big flat-screen TV. The Society of Motion Pictures and Television Engineers (SMPTE) offers guidelines for TV size that recommend a viewing distance of 1.87 times the size of the flat-screen TV.
Measure the distance from the entertainment center or TV stand where the flat-screen is located to the sofa or main seating area. For example, the distance might be 8 feet, which is 96 inches.
Divide 96 inches by 1.87, which is the factor recommended by the SMPTE. The result is about 52 inches, which is the society's recommended flat-screen size for a viewing distance of 8 feet from the TV.
Calculate the proper distance to sit from the TV by multiplying the screen size by 1.87. For example, a 42-inch screen size multiplied by 1.87 equals 78.54 inches. Divide this measurement by 12 to arrive at a distance of approximately 6 1/2 feet from the TV to the optimum spot for sitting.