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Calculates the number of agents required to handle the busy-period call traffic, given a percentage of calls that might receive a busy tone.

Can be used to calculate the number of agents required to service a given number of calls and meet the service level agreement.


AGENTSB(w, y, z) 


  • w: service level agreement, defined as the percentage of calls that do not get blocked
  • y: arrival rate of calls or number of calls per unit of time for the designated busy period
  • z: the average call duration during the designated busy period


Input Format Output Format

w: number (percentage)

y: number (time unit)

z: number (time unit)

No Data


The function uses the following arguments:

  • w: Number - Numeric line item, property, or expression
  • y: Number - Numeric line item, property, or expression - Must match the unit as used for argument z
  • z: Number - Numeric line item, property, or expression - Must match the unit as used for argument y


The function has the following constraints:

  • All parameters are mandatory.
  • All parameters must be a numeric line item, property, or expression.
  • Time unit used for the y and z parameters must be the same.
  • Result line item must be numeric.
  • Maximum number of agents is five million.

Excel equivalent

  • No Excel equivalent

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In this example, we have four call centers each covering a separate geographical area:

  • Each call center must achieve a service level agreement (SLA), expressed as the percentage of incoming calls that do not receive a busy tone and get blocked.
  • The arrival rate of incoming calls and the average call duration for busy periods are known for each call center from historical monitoring of operational performance.

With the baseline metrics entered for each call center in numeric source line items for Service Level Agreement, Arrival Rate Busy Period (calls/sec), and Average Call Duration Busy Period (sec), we can use the AGENTSB function in an Agents for SLA - Busy Period numeric result line item to calculate how many agents are required for each call center during the busy period to meet the SLA:

Example 2

This second example develops Example 1 to use the AGENTSB function to perform what-if analysis for determining how many extra agents are needed to handle increased call arrival rates during the busy period. A second Increased Arrival Rate - Busy Period (calls/sec) source line item is introduced for entering the increased arrival rates. The Agents for Increased Call Rate - Busy Period result line item gives the number of agents needed to handle the increased call rates during busy periods while maintaining the SLA:

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