[AV Media Matters] playing times

[c.s.woods@dorset-cc.gov.uk]

Can someone please give us some guidance about standard playing times for 8mm
and 16 mm film, by length.  In other words, how long would you expect a
film to
run if it is a 50 foot reel of 8mm and if it is a 350 foot reel of 16mm.  Are
there any standards?
Thanks for your help.

Moderators Comment: There is a standard formula for this that is in almost
all intro to film production books - I can't get my hands on quickly to
answer the question so I am posting this - perhaps of more utility there
was a company that made a very nice ruler that you would align to the core
and it would tell you the length.  I have not seen one in years.  Anyone
know where you can get one (or if you can)?

Also : apologies to the list - I have been a bit out of circulation this
past week so postings have not been prompt.
jim