In the 1920s, Danish mathematician Erlang created the eponymous formula. A pioneer in queuing theory, his work is still the foundation of any network analysis and switchboard staffing.

The formula is a complex equation taking into account the number of call agents available at any given time, the number of calls waiting and the Average Handling Time, as well as adding a value for random arrival of calls into the contact centre. It is still the main tool used today to calculate how much staff a contact centre needs to keep waiting times within targets.

Waiting time is often the main chief of complaint from customers so it is one of the most important things to get right. With an Erlang calculator, you can remove the guesswork and have the right number of operators at all time, without under- or over-staffing.

However, it is important to note that the results need slight tweaking. For example, the formula assumes that there are no lost or abandoned calls, which would have been the case in the 1920s as there were far fewer phones, but doesn’t reflect reality in today’s busy call centres. We recommend that you check your statistics for abandoned calls so that you can decide how to adjust numbers accordingly.

Another area that shows Erlang’s age is that it struggles to handle the variety of tasks and communication channels available nowadays as it was primarily devised to calculate staffing needs for inbound calls only. Today, a call centre is likely to regroup both inbound and outbound calls. Staff are also likely to manage other interaction with customers such as emails, social media and webchat. There again, Erlang results need to be moderated.

You also need to apply shrinkage -i.e. the percentage of staff not actively working because of bathroom breaks or illness for example – to the numbers the Erlang calculation comes back with. A good way to check how much variation there is between its number and reality is to compare its result with your own statistics.

Another important point to remember is that even the smallest variance can translate into huge differences in staff number so they shouldn’t be ignored.

If you are looking for a dedicated contact centre, contact Corporate Connect on 0800 230 000.