It takes up roughly half the on board storage a Switch has out of the box.
Super Smash Bros. Ultimate looks to be an utterly and absolutely massive game, bringing together six dozen characters, three hundred stages, nearly a thousand songs, and over a dozen game modes (including a great adventure mode). You would expect this game to be massive, and take up a healthy chunk of storage space.
And you know what, for a Switch game it will. The updated console eShop page for Super Smash Bros. Ultimate on the Switch shows that it will come in at 13.6GB, which actually makes it one of the larger Nintendo games for the Switch in terms of file size, along with The Legend of Zelda: Breath of the Wild and Xenoblade Chronicles 2.
The file size here will take up about half of the total available space on a Switch by default (a Switch comes with 32GB of on board storage, but only 26GB of this is available to the user. If you are planning on getting the game digitally, it might be best to invest in a microSD card.
Super Smash Bros. Ultimate launches exclusively for the Nintendo Switch on December 7.