Visual Erlang explorer

Drag the number of agents and watch service level, average speed of answer, occupancy — and abandonment — move live. Leave patience blank for classic Erlang C; add an average patience and it switches to Erlang A, modelling callers who give up. The quickest way to feel the service-level curve, the “power of one,” and the occupancy trade-off.

What you’re looking at

The green line is service (in Erlang C, service level; in Erlang A, the share of callers actually served). The amber line is occupancy. As you add agents, service climbs — steeply at first, then flattening — while occupancy falls, because the slack that gives callers a fast answer is the same slack that leaves agents waiting. Near the steep part of the curve, a single agent up or down swings the result dramatically: that’s the power of one, far more pronounced on small queues than large (the pooling effect). The amber line is why occupancy is an output, not a target — pushing it up means moving left, into the fragile zone.

Add an average patience and the purple line appears: abandonment. Erlang A is more realistic than C — because some callers give up, you often hit the same service with slightly fewer agents. For finite lines and redials too, see the Erlang X calculator.

Maths: Erlang C and Erlang A, the same engines behind the Erlang C and Erlang A calculators.