From the exterior of the frame, it measures 7.5" diameter.  The diameter of the mirrored portion is about 4" diameter.  This is a nice little piece I found on the second-hand market that hung in a wall display in my home for many, many years.  I like earthy things, and it has super good energy, but I live near a swap meet and an auction house so my decor tends to change pretty often.  YOU KNOW.  I have to laugh.  

If you like earthy, boho, industrial or just need a little more light reflected around the room, this is a good choice!