Work out erlang c agents instantly with clear inputs, formula shown and shareable results.
Erlang C models a queue where callers wait, giving the probability of waiting and from that the service level: the share answered within the target. The classic 80 percent in 20 seconds target follows from these formulas. Note how steeply the answer time falls as agents rise past the offered traffic — the last agent or two buys most of the service level.
Erlang C
C = B / (1 - (a/N)(1 - B)); service level = 1 - C x exp(-(N - a) x target / AHT); ASA = C x AHT / (N - a)
Otherwise the queue is unstable and grows without bound. Agents must be strictly greater than the traffic in erlangs for any finite wait time.
Caller abandonment, retries, agent breaks and non-Poisson arrival patterns. It tends to overestimate the agents needed because it assumes nobody hangs up.