How do I know how much DPI the device has?

Question

How do I know how much DPIs a device has (and thus if it's ldpi / mdpi / hdpi / xhdpi, - and screen size, which is also measured in dp - xlarge / large / normal / small - according to http://developer.android.com/guide/practices/screens_support.html)?

I know the device's resolution and diagonal size, for example:

Display TFT LCD, 3.5 in (89 mm) diagonal.

320×480 px HVGA with Gorilla Glass

16M colors

(Taken from http://en.wikipedia.org/wiki/Samsung_Galaxy_Ace)

Don't need it programmatically, just to calculate myself.

Answer 1

Use DPI calculator to calculate dpis, and Figure 1 in the dev docs to determine whether its ldpi, mdpi, etc.