I have made a queue calculator for you
It’s based on the formula that the length of queue will be U / (1-U) where U is the utilisation of the serving resource. Utilisation is the amount of time spent working divided by the amount of time available ~ which can also be calculated by the arrival rate divided by the service rate. And then the waiting time will be the queue length multiplied by the time taken to serve someone – on average. Management usually want utilisation to be between 80% and 100% but that can have a disastrous effect on queue lengths = waiting times. Have you ever been to A&E in a hospital, or an airport check-in??
Anyway, don’t worry about all that, just play with the sliders!
One thing to know when using the queue calculator: a NEGATIVE queue or waiting time means INFINITE – the queue will get longer and longer = total disaster!
OK: let’s play:
Three recommended things to try:
a) what if the arrival rate increases a bit – see how the queues get MUCH worse with even just a few more arrivals per minute
b) try increasing the time it takes to serve a customer, for example if you added an extra bit of bureaucracy to your system – see how much the queues increase! And of course if you could reduce the time a bit, how much better the service becomes.
c) try getting rid of a person – as long as the numbers don’t go negative it means that your people can cope, …but see how much longer the queues get!!
PS – You can think of the above sliders as “people per hour” or “per day” instead of “per minute” if you prefer – the numbers work just the same