Place or hold the measuring tape along the top or bottom of the television and record the number on your note paper.
Measure the width or height of the TV from top to bottom and record the number on your note paper. Be sure to take this measurement at the widest point. Some TV sets have curved or bowed edges surrounding the screen.
Measure the depth of the TV and record this number in your notes. This will tell you how thick your flat-panel TV is or how deep your cabinet must be to hold an older model television.
Measure the screen by placing one end of the measuring tape in the upper left corner of the screen and running the tape diagonally down across to the lower right corner. This is how manufacturers determine the size of the screen itself.