http://www.ign.com/articles/2016/06/...light-princessE3 2016: ZELDA: BREATH OF THE WILD’S OPEN WORLD IS 12 TIMES BIGGER THAN TWILIGHT PRINCESS
E3 demo represents just 1% of the game’s world map.
Nintendo has revealed that the open world in The Legend of Zelda: Breath of the Wild is 12 times larger than the map in Twilight Princess.
During a presentation at E3, Nintendo also revealed that the demo of Breath of the Wild shown at E3 -- which contains a large portion of open field as well as several enemies, Shrines, and more -- represents just 1% of the game’s total size.
http://www.neogaf.com/forum/showthread.php?t=1234095
Pretty big.