Mobile phone manufactures/retailers appear to be confused. Their literature quotes Screen Size as a Resolution not a physical size. Phones with the same resolution 176 x 220 have different physical sizes from 1.9" to 2.8 vis".(diagonal measurement). Mobile phone manufacturers and retailers may well be breaking UK laws by publishing the screen size as a resolution not physical size.
Sizes 1.8"/47mm to 2.2"/56mm covered 80% of phones, measurements taken off phones in shops.
As an Industrial Designer, I fail to see why most phones have a width to height ratio of 4:5 and 3:4. Screen widths sholud be Standardised to 176px for phones and 240px for Pda's so pictures and tables can be sized. The height can be any dimension.