Measure the screen diagonally from one corner of the visible display to the opposite corner (corner to corner).
Exclude the TV’s bezel/frame if it’s separately defined; measure the visible screen area.
Use a tape measure or ruler; keep it straight along the diagonal.
Record the measurement in inches (or convert from cm: inches = cm ÷ 2.54).
If you need the width/height instead of size, measure the screen’s visible width and height separately.
Verify whether the TV is marketed by diagonal (most are) and use the diagonal measurement for “TV size.”