Model for Shift Planning. The Danish mathematician Agner Krarup Erlang develops the formulas Erlang B and Erlang C, named after him.
The Erlang C formula is used to determine a service level based on call volume, number of agents and average processing time. Frequently Erlang C is used to determine the number of agents, i.e. the personnel planning, based on a service level to be reached.
Erlang B provides a formula for determining the line capacity.