I wear a size 6-6 1/2 in women. if i was to get UGG boots, will i need a 5.?

just curious ... a lot of ppl say that UGG boots run small and they stretch. so i was wondering, if i was to get some (i wear a size 6-6 1/2regularly) ... will i need a size 5 in those boots.??? (I want the clic cardy ones.) and those are sweater material.