Is the tallest mountain in the world mt Everest?
However, the Hawaiian mountain of Mauna Kea is in fact higher, if one counts the fact that it is an island. Mauna Kea measures over 10,000 meters tall above the sea floor from which it rises, theoretically making it taller than Mt Everest. If measured from sea level, it is only 4,205 m, or 13,796 feet, tall.