Erlang C Calculator

Calculate the ideal number of agents needed to meet your service level goals

Calculator Inputs

Total inbound calls expected per hour

Average talk + hold + after-call work time

Percentage of calls answered within target time

Maximum acceptable wait time for calls

About the Erlang C Formula

The Erlang C formula is used in call center management to calculate the minimum number of agents required to handle a given volume of calls at a specified service level. The formula accounts for random call arrivals and variable call durations.

Erlang C = (u^n / n!) / [(u^n / n!) + (1 - u) × Σ(u^k / k!)] Where: - u = Traffic Intensity (calls/hour × AHT in hours) - n = Number of agents - ASA = (Pw × AHT) / (n - u) - Pw = Erlang C result

Key Metrics:
• Traffic Intensity: Total call volume in Erlangs (1 Erlang = 1 hour of continuous traffic)
• Occupancy Rate: Percentage of time agents are busy (should stay below 85%)
• Pw (Probability of Waiting): Chance a caller must wait in queue
• ASA (Average Speed of Answer): Average wait time before answer

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