Mount Everest is one whopping big mountain, but is it the tallest in the world? In fact it is not. A mountain is highest in regard to how far it soars above sea level. But technically it is tallest from base to summit. And Mauna Kea kills it at being the tallest.
Here's the deets: Above sea level, Mauna Kea (in Hawaii) is only 13,799 feet (4,206 meters). But when you count the crazy enormous portion of it that's underwater, it's 33,465 feet tall (10,200 meters). Everest, that snobby little upstart, is only 29,029 feet (8,848 meters) above sea level, with none of it below sea level [source: Mitchinson and Lloyd].
But the shame doesn't end there. Mount Kilimanjaro hasn't taken the stand yet. Kilimanjaro is 19,340 feet (5,895 meters) top to bottom. So it's not as tall as Everest – but Everest is surrounded by the rest of its friends, the Himalayas, all of which are collectively growing by a quarter of an inch per year and pushing Everest's summit higher. Kilimanjaro, on the other hand, is solitary, rising out from the relative flatness of Tanzania all on its dramatically striking own [source: Mitchinson and Lloyd].