Erlang C calculator

From time to time I need to evalute trunk usage.
There are many possible ways on how to do it (ask provider, enable PBX traffic measurements).

Another way is to use Erlang-C formula.

Some of the sites that I use for it.

http://erlang.com/calculator/erlc/       - web-based
http://owenduffy.net/traffic/               - web-based
http://www.lokad.com/calculate-call-center-staffing-with-excel      - excel file

Thanks to the creators of these very helpful resources!

I've slightly modified Excel calculator for my own needs:

erlang_c_calculator_2014.xls

If you use E1 trunks instead of T1 just change 23 to 30 in "Trunk usage" column formula.