Depends on whose back they are on. Normally in mountain climbing, the big loads start at 50 pounds and go to about 90 (after that, the climber is lying... which is perfectly acceptable). These are the loads a guide might be carrying in Alaska on Mount McKinley, a peak known for the big packs people carry. Everest is not a mountain for big and heavy packs. Muscles need Oxygen and they rarely get enough of it on Everest. As the altitude gets extreme, the amount one can carry is greatly reduced. So a heavy pack at 25,000 feet might be forty pounds. At the summit (29,000 feet) a heavy load would be one oxygen bottle and granola bar, about 15 lbs.

—Dave Hahn, Climber

EVEREST FAQ