Haven't you ever wondered what would happen if you click on that button in the upper right corner of the Entity Info window?
Here's a circle, unexploded, and you can clearly see its length or circumference.
Screenshot - 11_9_2017 , 4_29_18 AM.png
It's also the circumference of the circle, not the sum of the lengths of the edge segments.
Screenshot - 11_9_2017 , 4_30_31 AM.png