Work out queue wait time instantly with clear inputs, formula shown and shareable results.
For a multi-server queue, Erlang C gives the probability of waiting and the average wait is that probability times service time divided by the spare server capacity. Queue length then follows from Little's law. The behaviour to notice is that wait time depends on the gap between servers and offered traffic, so the same utilisation is far more painful with few servers than with many.
M/M/c waiting
traffic = arrivals x service time / 3600; average wait = C x service time / (servers - traffic); queue length = wait x arrival rate
Economies of scale in queueing. Twenty servers at 90 percent utilisation have twice the absolute spare capacity of ten at 90 percent, so bursts are absorbed faster.
Yes, Poisson arrivals and exponential service times. Bursty arrivals produce longer waits than the formula predicts.