Climbers typically ascend only part of Mount Everest’s elevation, as the mountain’s full elevation is measured from the geoid, which approximates sea level. The closest sea to Mount Everest’s summit is the Bay of Bengal, almost 700 km (430 mi) away. So to approximate a climb of the entire height of Mount Everest, one would need to start from this coastline, a feat accomplished by Tim Macartney-Snape’s team in 1990. Climbers usually begin their ascent from base camps above 5,000 m (16,404 ft).
It’s obvious once you think about it, but at what point would you consider it in daily life?
I believe the term for height from base is called prominence. The highest one can climb is Denali in Alaska, at around 5500m. Obviously omitting mountains that have their bases on the ocean floor like Mauna Kea ofc.
Prominence is a bit more complicated than that. It refers to the height of a mountain or hill’s summit relative to the lowest contour line encircling it but containing no higher summit within it. Everest’s prominence is actually still its height above sea level.
Everest is a bit unique in that regard since, as the highest peak, by definition it can’t have any higher peaks within any contour around it.