How big is small, normal, large and xlarge?

Question

I know that there is a section in http://developer.android.com/guide/practices/screens_support.html about the categories of the physical screen sizes but the diagram is very rou

Answer 1

To elaborate on John Boker's answer...

xlarge screens are at least 960dp x 720dp
large screens are at least 640dp x 480dp
normal screens are at least 470dp x 320dp
small screens are at least 426dp x 320dp

And since 160dp approximately equals 1in on every device:

Density-independent Pixels - An abstract unit that is based on the physical density of the screen. These units are relative to a 160 dpi (dots per inch) screen, on which 1dp is roughly equal to 1px.

http://developer.android.com/guide/topics/resources/more-resources.html#Dimension

The physical sizes can be calculated approximately as follows:

xlarge screens are at least 6in x 4.5in
large screens are at least 4in x 3in
normal screens are at least 2.9375in x 2in
small screens are at least 2.6625in x 2in