The carat weight of diamond simply refers to the weight of the stone as it is measured on a diamond scale in units of carats as opposed to grams or pennyweight. The metric carat = .200 gram or 1/5 of a gram.  To really get an accurate idea of just how big these sizes are in carat weight, it is best to go and shop a few jewelry stores and see em for yourself.   While you'll be accurately seeing the clarities, colors, and cuts here on this site, you can not yet try on a diamond engagement ring over the Net (not yet anyway)    ;)

These are some of the pics usually shown in diamond literature to represent various "carat weights", but this is pretty lame if you ask me. Go and have her try em on, but before you have your girl start trying on different sizes in carat weight to see what she likes, finish the crash course here, so you get an idea of how much these things cost!  This way you can "suggest" ;) what sizes you may want her to try on.  You will find it is very easy to have a girl fall in love with a diamond that is waaaay out of your price range! ;)  Clik "next" to proceed.