Depends on if it's a UK/US size 12. A UK size 12 is way smaller  than the US one I think (cause of vanity sizing). Most shitladies are between 0-8/10 I think? Depends on vanity sizing, what type of clothes+body shape. A lady with a bigger bust or wider hip will need a bigger size. Unfortunately that means clothes will often hang in an unflattering manner around the waist or legs (unless it's stretchy and tight). I usually wear something bigger for my shoulders and bust, and things just bag around the waist.