I have a whole bunch of rolls of S16mm film from a project of undetermined length. The rolls themselves are all of varying length -- short ends joined together at the lab during processing into rolls of varying sizes. I need to figure out how much film I have in total.

**Is there an equation which relates the radius of a roll to its length?**

That is, if a particular roll is 12 inches in diameter, is there any formula that tells me I have roughly, say, 700 feet of film on the roll?

Any thoughts would be appreciated.

Thanks!

The problem is, your answer is going to depend on how tightly the film is wound on the roll.

If you have access to a set of reasonably accurate digital scales, you could weigh a short length of film (say 10 feet) and then divide one-tenth of that into the total weight, minus the weight of the core, to give an answer in feet. That would probably be as accurate a way as any.