Fallout 4 on Xbox One clocks in at 28.12 GB
The Fallout 4 product page has been updated with install size info. The game clocks in at 28.12 GB. All in all, that doesn't seem like a massive game. Bethesda has worked some magic in the past with slim installs of games like Skyrim, which fit on one Xbox 360 disk and other seeming feats of magic.