How big are Ancalagon the Black and Smaug? (Contrast)
Ancalagon is bigger than The Smaug, since they crossed the three mountains.
With this information, it's safe to say Ancagalon has several size comparissons.
Ancalgons are roughly the size of Thorondors.
Ancalgon was the largest creature in Middle-Earth, according to many sources.
While The Atlas of Middle-Earth describes Smaug as 20m long.
Ancalgon would win because he is bigger and can breathe fire.
For more information between Ancagalon and Smaug, CLICK HERE.
For more information between Ancagalon and Smaug, CLICK HERE.