Someone on Reddit was wondering how many kegs a cylinder of CO2 would carbonate. Using some constants from Wikipedia and absolutely no gas expansion temperature correction I made a quick spreadsheet to estimate the number. Feel free to play with the input numbers to fit your situation. Here it is!
The gas density constant I used was calculated @ 32F, and with most kegerators being in the low 40s I figured this was close enough.
The “too long, didn’t read it” answer: for a 5 pound tank you’ll be able to force-carb about 17 5-gallon batches @ 2.5 volumes.
Below are the full equations I used.