I usually measure them first. Like the charms...5" might mean from valley on one side to peak on the other. I learned that the hard way. I made a quilt that used 5" charms and I did it in sections with a middle section. Well, the sides didn't match up and I found out it was because the 5" charms needed to be measured from valley to peak. So that's how I know and why I measure now. I never did fix that quilt. I used 3 charm packs on it and would have had to rip the whole thing out and I was so upset when I realized what I did, that I just folded it all up and put it away and figured someday I might feel like ripping it apart and starting over. That day hasn't come yet and it's been about 4 years now.