Small, Medium, Large Dress Sizes
Many shops now use letters for their sizes, with the following meanings S - Small, M - Medium, L - Large and X - Extra. This sizing system is called dual sizing by some stores and brands. Sometimes you will see XXS meaning Extra Extra Small or Double Extra Small (i.e. Smaller than Extra Small) or XXL meaning Extra Extra Large or Double Extra Large. With the large sizes the number of Xs can reach 4 or 5.
With these sizes there is significant variation between stores (see our Size Guides page) but the most common sizing is for an XS to be equivalent to a UK 4-6 or US 0-2 up to an extra large being equivalent to a UK 20-22 or US 16-18, however some brands use a single size gap between sizes so an XS can be as large as a UK size 8 or US size 4 and an XL as small as a UK size 16 or US size 12 so make sure you try things on if the dress is only marked with a lettered size.
S,M,L Sizes - Average Size Guide
Using Small, Medium and Large sizes with X for Extra is often known as dual sizing because usually Small, Medium and Large each equate to two UK, US or European sizes. This was done to cut down on the number of manufacturing runs for different sized garments and reduce manufacturing costs. Owing to the larger difference between sizes you may end up not being able to find a good fit, for example Small could be slightly too small and Medium slightly too large.
Dual Sizing Equivalents Table
The folowing table gives the usual equavalents for the dual sizing system for US, UK, German, French and Italian sizing systems.