The achievable packing density on a reel (bobbin or flanged drum) is dependent upon the care taken during wrapping.
In theory, all reels have a capacity of 100%, but such a packing density is rarely possible.
A good fleeting (or spooling) facility (guidance system) should produce between 85% and 95%. Careful packing by hand should achieve between 75% to 85% and between 60% and 75% with rough wrapping.
You may use any units you like, but you must be consistent.