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 rough. When a screen stop normal and fall under the large category? etc. I mean specifically the physical dimensions, not the dpi. What are the specific limits to the screen sizes in the categories?

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

Answer 2

In my experience, there are no "specific limits" to the screen sizes using the small, normal, large, x-large notation. They are more general and will get you by in the majority of cases. These values are part of the rom on the device, so it's up to the manufacturer to conform to the standards in the API documentation or not.

If you are targeting API 13+, you can use the sw-dp notation to get more specific (see http://developer.android.com/guide/practices/screens_support.html#DeclaringTabletLayouts).