While measuring mountains may not seem like rocket science, there are actually a number of different ways in which to measure mountains. Depending on which technique is used, the title of world's tallest mountain could go to several different mountains in various regions of the world. Some scientists will also heatedly debate the issue, arguing that their technique is the accurate, conventional, and widely accepted one.

When most people think about the elevation of a mountain, they often visualize elevation from sea level, which is also one of the most widely accepted measuring techniques used when determining the world's highest mountain. People are familiar with sea level measurements because elevation is classically expressed as a distance from sea level on road signs, maps, and textbooks. This is also an easy form of measurement to visualize. When measuring from sea level, Mount Everest is the uncontested king, with a peak which is 29,035 feet (8,850 meters) above sea level.

However, Mount Everest gets quite a leg up, as it were, since it is situated on a high plateau, and the height of the plateau is included in the height of the mountain because the plateau is above sea level. For people more interested in vertical rise above sea level from the base of the mountain to the top, Mount McKinley would be considered the tallest mountain in the world, because while the maximum elevation of Mount McKinley is lower than that of Everest, the vertical rise is 18,000 feet (5,500) meters, in contrast with Everest's more paltry 12,000 feet (3,700 meters).

However, some people prefer to measure mountains from their base, whether or not the base is above sea level. Measuring from its base, Mauna Kea is the world's tallest mountain, due to the fact that the base is deep under water on the bottom of the Pacific Ocean, making the distance from the ocean floor to the top of the mountain 33,476 feet (10,203 kilometers), which beats out Everest even if the mountain's elevation is only 13,796 feet (4,205 meters). Another contender using this measurement is Mount Lamlam, with a base deep in the Marianas Trench, and differing reports of a measurement from base to top; the most extreme claims state that it is 37,820 feet (11,527 meters), which would make it higher than Mauna Kea and the world's tallest mountain according to a measurement determined by the height from the base to the top.

For those who would prefer to measure from the center of the Earth, the world's tallest mountain is Chimborazo, which is 3,968 miles (6,384 kilometers) from the center of the Earth, although the mountain's elevation is 20,565 feet (6,268 meters). This method of measurement may be a bit more abstract than most people prefer, unlike measurements based on sea level or base, which use concepts which people can easily visualize.