Erlang formulas

A set of industry-standard formulas which allow you to model the relationship between staffing, call volume, and response time. For a given set of inputs, these formulas yield a number of required agents.

Making sure you have the right number of support agents to quickly and reliably help customers is a critical component of workforce management. As a support leader, you need to consider the number of agents you have at your disposal, the number of customers you serve on a daily basis, and the average time it takes agents to respond to customer queries.

One of the best ways to effectively plan your call center staffing needs is to use the Erlang C formula—a technique almost as old as telephones themselves. Intimidated by math? Don't worry, we did it for you with our free, easy-to-use online Erlang C calculator.

Why is Erlang C useful?

At its core, Erlang C allows you to model the relationship between staffing, call volume, and response time. These are factors that good support managers understand intuitively, but a little math goes a long way toward quantifying those intuitions.

Most often, Erlang C is used to estimate required staffing for a given target response time and expected amount of contact volume. For more on how to estimate the latter, see our blog post on how to forecast for customer support. Many online Erlang C calculators also factor in variables like shrinkage, occupancy, and concurrency. These additions make the formula flexible enough to model modern real-time channels like chat, SMS, and social media in addition to phone calls.

‍Note that in this post, we focus on staffing real-time channels. Erlang C is typically not appropriate for modeling channels like email, where response times may be in the hours or days and a backlog of tickets can build up over time.

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