http://wccftech.com/fifa-18-download-size-nintendo-switch/

Given the limited internal storage space that Nintendo Switch has, surely you must be interested to know how much space the digital versions of all the titles will occupy. If one of the launches in which you have the target is FIFA 18, we would like to inform you that Nintendo has already revealed its file size.

The page of FIFA 18 on the Nintendo UK site indicates that the download size of FIFA 18 is of 14301.53 MB; that is, just over 14.3 GB. It is important to note that this size only refers to the initial download of the game and, therefore, it is possible that FIFA 18 will receive some type of update on its day of release.