Estimate Number of Telephone Lines

Use the following to estimate telephony traffic items using an Erlang B algorithm.  It can also be used to determine how many checkout points are needed in a supermarket.

Enter three items and calculate the fourth.

Number of calls in the busiest hour
Average duration of a call in seconds
Percentage of calls blocked
Lines  

Notes

Simply stated, the Erlang B algorithm calculates the percentage of calls blocked whereas the Erlang C algorithm calculates the percentage of calls that will be waiting to be answered and assumes there is a queue in which the calls are held before being answered.

Another way of stating this is that the Erlang B algorithm calculates the percentage number of callers who get a busy tone whilst the Erlang C algorithm calculates the percentage number of callers who have to wait to be answered.

For a more sophisticated way of performing an Erlang C calculation please go to https://www-ens.iro.umontreal.ca/~chanwyea/erlang/erlangC.html

Posted on 1 January 2019 by Graham Lawrence