Please note that this is the Narutopedia's article on Naruto Uzumaki's version of the technique. If you are looking for the article on Jiraiya's version then you should head to Ultra Big Ball Rasengan.
The Sage Art: Ultra Big Ball Rasengan is a gigantic Rasengan created by Naruto Uzumaki, enhanced with sage chakra. Although its destructive effects have not been seen, it was used to distract Kurama. Presumably, it is as strong as Jiraiya's version which was said to be able to carve away a mountain if it exploded.