There’s a big difference between tallest and highest mountain. Mount Everest is the highest mountain but not the tallest mountain in the world. Tallest measures from the base of the mountain to the peak. Highest measures the height of the peak. The tallest mountain in the world is Mauna Kea in Hawaii. Additionally, Ecuador’s Mount Chimborazo is the mountain peak farthest from the earth’s core and closest to the sun due to the earth’s centrifugal bulge.