I bought these one size larger, since that's what they usually recommend for regular boots.  Glad I did!  I usually wear a 6 and got a 7.  They're perfect.  I have a slightly wide foot in front, and a 6 would've been too tight.  I walk the dogs on grass in the mornings, and even going up and down steep hills these grab the wet grass amazingly well.  I was impressed.  They really do seem to be waterproof as well. Really cute, too.