Cumulative elevation gain
In cycling, hiking, mountaineering and running, the term cumulative elevation gain is the total of every gain in elevation made throughout a journey. Elevation losses are not counted or offset against this measure. Cumulative elevation gain, and the total distance of the journey, are two key metrics used to quantify the physical demands of a journey.
Calculation
In the simplest case of a journey where a climber only travels up on their way to a summit, the cumulative elevation gain is the difference between the summit and starting elevation. For example, if they start a climb at an elevation of and continue up to a summit of then their CAG while standing on the summit is . In descending from the summit to return to their start they don't have to make any other gains in elevation, so their total CAG for the journey stays at, which is the total of the vertical distance they climbed.Now take the case of a journey where a climber travels across several summits with more "ups-and-downs". For example, consider two mountains whose summits are both at in elevation, and between them is a low point at an elevation of. If a climber starts their journey at an elevation of, their CAG is by the time they reach the first summit. They then drop down to the low point between the summits and have to gain another to get to the top of the second summit. On the second summit, the climber has a CAG of . To return home, they have to drop back down to the low point at and then gain another to get back to the first summit. Now they have a CAG of . In descending from the first summit to return to their start they don't have to make any other gains in elevation, and their total CAG for the journey stays at.
CAG captures the effect that travels on terrain with a lot of "ups-and-downs" that will result in a lot of vertical climbing.