It measures more round than it looks. 18 1/8" widest point x 16 1/2" narrowest point x 5" tall. I guess the grain magnifies the oval look, but 1 5/8" out of round is still pretty impressive to me. Glad I kept the wall thickness around 5/16" so it would "give".
Wowsa -- that's one fast growing tree! I only see 17 years of growth from this view. If an 18" bowl only has about 20 years of growth, you could probably hear that one growing.