What is Erlang C?
Erlang C is a mathematical formula used to calculate the number of agents needed to handle a predicted call volume while meeting service level targets. Named after Danish mathematician A.K. Erlang, this formula accounts for call arrival patterns, average handle time, and acceptable wait times to determine optimal staffing.
Erlang C Inputs
To calculate staffing with Erlang C, you need:
- Call volume — Number of calls expected per time period
- Average Handle Time — Talk time + after-call work
- Service level target — e.g., 80% answered in 20 seconds
Erlang C Limitations
Erlang C assumes:
- Callers wait indefinitely (no abandonment)
- Random call arrival (Poisson distribution)
- Infinite queue capacity
For real-world accuracy, WFM tools apply adjustments for abandonment, shrinkage, and agent availability.
Erlang C in Practice
While the math is complex, modern workforce management tools automate Erlang C calculations. You input your forecast and service level goals; the system outputs required staffing.
Platform28 integrates with WFM tools that handle Erlang C calculations automatically. Learn more.
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