Mauna Kea (in Hawaii) is the world's tallest mountain peak. When measured from the ocean floor to its summit, it's 33,476 feet tall (10,204 meters), but only its top 13,803 feet (4,207 meters) extend above sea level.Mauna Kea is also the world's tallest volcano.allest mountain from sea level (highest): Mount Everest (also known as Qomolangma, or Chomolungma) in Asia's Himalayas is the world's highest mountain peak. When measured from sea level to its summit, it's 29,029 feet (8,848 meters) tall.