Call center calculators are used to improve call center performance by determining the staffing requirement of a call center for different times of day and days of the week.

For inbound or outbound contact centers to work effectively and achieve the objectives of the company, they must have the appropriate number of resources to reach certain specified targets. Outbound call centers that set the number of planned calls per hour will need to consider metrics, such as average call duration, to determine the number of agents needed. For inbound call centers, the process of staffing involves establishing a traffic model that considers the number of expected calls per hour and service level targets to determine how many staff members are needed at different time periods throughout the day.

The business must also factor in other relevant information, such as the arrival rate of calls per week, the average number of hourly calls they receive, and the average handling capacity of each agent. Factoring in the typical call volumes, average wait times, and the average call load that call center agents are able to handle will help you to determine the number of lines required, the number of agents required, rate of abandonment, and how to schedule shift coverage to meet your service level targets.


The Bright Pattern call center calculator is based on the Erlang calculation model, and it helps you to estimate the number of call center agents you need in your call center.

For the staffing calculator to properly estimate the number of call center agents required, certain basic information about service level, call abandonment, and average speed of answer is required:

  • Average Handling Time (sec): The average length of time, in seconds, that handled or completed calls last (e.g., “180 sec”)
  • Minimum Service Level (%): The minimum percentage of service calls required to be answered in a specified timeframe (e.g., “80%”)
  • Service Level Interval (sec): The length of time, in seconds, allotted to service calls (e.g., “20 sec”)
  • Average Patience Time (sec): The average length of time, in seconds, that elapses before the call is abandoned  (e.g., “180 sec”)
  • Max Abandonment Rate (%): The maximum percentage of calls that can be abandoned by the caller (e.g., “5%”)
  • Max Average Speed of Answer (sec): The average time, in seconds, that calls can wait in the service queue before being answered (e.g., “10 sec”)

You can enter this information in our staffing calculator by clicking the “Change Input Parameters” button. Then the call center staffing calculator will summarize the daily call center staffing results.



One of the advantages of call centers is that they help companies save money and drive more revenue. In order to optimize their performance, call centers need to schedule staff according to their needs and goals. Call centers with excess staff will have unnecessary expense, while call centers that are understaffed will create a situation where staff members are unable to meet certain service level targets, such as the time to answer an incoming call. As a result, understaffing will undermine the objectives of the call center and keep the organization from effectively satisfying callers.

Let’s say we input the following information:

  • Arrival call rate: 2 calls per second, or 7200 calls per hour
  • Average handling time: 3 minutes, or 180 seconds
  • Number of agents: 180

According to the Erlang calculator, this system is unstable and no service objectives could be evaluated. However, consideration of call abandonment makes this system stable.

Using the calculator, we get the following information:

  • Service level = 77.4%
  • Abandonment rate = 0.55%
  • Average speed of answer = 0.84 sec
  • Agent occupancy = 98%

With this information, we know that the system will work and only 0.55% of all calls will be abandoned.

Let’s say we input the following information:

  • Arrival Call Rate: 1 call per second, or 3600 calls per hour
  • Average Handling Time: 3 minutes, or 180 seconds
  • Average Patience Time: 180 seconds
  • Number of Agents: 181

Using the calculator, we get the following information:

  • Service level = 63.3%
  • Abandonment rate = 1.37%
  • Average speed of answer = 2.13 sec
  • Agent occupancy = 98%

If we exclude abandonment (e.g., set Average Patience Time to infinity), we get Average Speed of Answer equal to 7.69 seconds, which increases waiting time threefold and dramatically lowers service level percentage to 46.7%. The calculator can provide valuable information about call abandonment, which, in turn, can be used to avoid overstaffing.


We are happy to answer questions, discuss specific workflows and requirements on a live presentation online, describe core benefits, or set up a pilot project to trial our applications without paying any license fees. Let Bright Pattern’s call center solution help you change the pattern of customer service