I think you get around 25 rolls. Using bulk is more for the flexability of winding shorter and custom rolls that way your exposures are basically the same situation and developement, consistant for all the shots on that roll. Otherwise you'll wind up with blocked up highs and others too flat or thin on the same roll.
I make my rolls around 15 or so frames and blow the entire roll on one subject.
You should get 18 rolls at 36 exp each. I do, at least. Depends, too on how long you make your leaders, and how much film at the end of each roll is light struck. Some bulk loaders have a shorter distance from the feed out opening to the cassette take-up crank opening, so the end of the film, where it is taped to the spool could have from 1 1/2 to 3 frames exposed to light, depending upon your loader.
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36 exp requires 54" plus leader and taped end. An 8" leader and end combined will make the total length 62". 100 ft = 1200". You should get 19 rolls if you are careful not to waste too much everytime you open the film loader. If I were bulk loading today I would make 12 exp rolls for the same reason as stated by others. I rarely use all 36 exp at one time. I cut the film in the camera in the darkroom and make a new tongue for the remaining unexposed film after I get the exposed film in the reel. It is a bother, but the films I buy from J&C are available as 36 exp only.
I have given up on bulk loading because reusing cartridges increases the chance of scratching film. IMO the time and effort required to make the exposures is worth a lot more than the small amount saved by bulk loading. The only reason I would bulk load today is if I found an unusual film available in bulk only.
I've always ignored bulk loading for the same reasons. But with future supplies of a chosen film possibly in jeopardy, bulk loading could be another way to stock up rather than lots of little boxes. Also shooting shorter rolls would mean less wastage as I write off any unexposed frames if I finish shooting before the roll is used. Might be worth considering again.