Hi,
Here's a pdf I made some time ago (I have uploaded it as an attachment, if it doesn't work let me know and I can email it to you). It shows film length vs time in 3-perf/4-pert and 24/25 fps. The first page is feet, the second meters. I had a printshop print cards on both sides and laminate them, got very neat indeed ;)
All time calculations are rounded off down to nearest second, so to be on the safe side. The length calculations at the bottom of each page are more precise so you can multiply them if you need to.
Hope this will serve you well. I made one for 16mm aswell, with a star chart on the back side, if anyone is interested.
David Gylje
35mm.pdf