What's the real length?

So, today I am 18 weeks along in my pregnancy. I get weekly emails from babycenter.com, and my one today says baby is 5 1/2 inches right now. However, the little timeline at the top of my blog says baby is 10 inches. That's a pretty big difference. I'm pretty sure I trust babycenter over this timeline, but it makes ya wonder.... So far everything is going great. I certainly can't complain. I posted a baby bump pic on facebook for those of you that haven't seen it yet. It's not that big yet, but I can tell it's there. My pregnancy has been super easy so far besides just feeling tired, and a little sick in the beginning... I never even threw up or anything. I feel really blessed and hope it stays that way even throughout childbirth! haha. We'll see! My next doc appt is today, and on the 25th is my ultrasound to find out if baby junior is a boy or girl. I think it's a girl, but I could be wrong. We can't wait to find out!