Is compressed volume a mostly meaningless number?


It depends on how you think about the question. Because many UL backpackers try to get away with the smallest possible pack size in order to save weight, they compress their sleeping bag until it is as hard and dense as a baseball (although bigger grin).

But, as far as a manufacturer's published number for "compressed volume" goes, there are zero standards for how to measure this, therefore no way to know what that number really means compared to another sleeping bag maker's number. In that case, yes, it is meaningless.