When you hear “42 inch HDTV” what do you think of?  Most people think of a fairly big TV, but don’t know for sure what they’re getting.  Some people realize that the “inches” refers to the diagonal length of a monitor, and HDTVs these days tend to have 16:9 aspect ratio (meaning the screen is about 1.78 times longer than it is tall–that said, the classic aspect ratio is 4:3, so not all “20 inch TVs” are the same size).  When shopping, a lot of people ask, what does that extra inch mean?  This week’s graph shows square inches of viewing space as a function of the stated inch-number on a TV (for a 16:9 aspect ratio).  Notice two things: first, an extra inch on a big TV results in a larger TV-watching-area increase than an extra inch on a smaller TV.  But that’s only in absolute terms.  The second thing to notice is that an extra inch on a 20 inch television results in a 10% increase in viewing space, while an extra inch on a 50 inch television results in only 4% increase in viewing space.

(Yes, I did the math myself…in Excel.)