Erlang calculator for contact centers

After-call work (ACW)

Working time spent by agents after the conversation with the customer is complete, which is directly related to that conversation, e.g. entering customer details in the CRM system, sending e-mails, and placing orders. Also known as 'wrap time'.

Agent

An employee in a contact center who is responsible for direct contact with customers, e.g. answering phone calls, engaging in web-chats, responding to emails, or customer posts on social media platforms. Also known by other titles such as 'advisor'.

Average handling time (AHT)

The average amount of time required to complete a single customer contact, e.g. a phone call or an e-mail, during a specified interval. Handling time includes talk time (see ATT), the time during which the customer was on hold during the call (see hold time), and after-call work (see ACW). Also known as 'average processing time'.

Average talk time (ATT)

The average amount of time during a call or other contact when the agent and customer are in conversation. Waiting time, hold time and after-call work are not included.

Call center

A business function in which a group of employees, commonly known as agents, are dedicated to the handling of telephone calls from and to customers. See also 'contact center'.

Calls

Individual telephone conversations. See also 'contacts'.

Contact center

A business function in which a group of employees, commonly known as agents, are dedicated to handling communications with customers via a range of channels, including but not limited to phone calls, web chats, emails, social media posts, and back-office processing of e.g. loan applications. See also 'call center'.

Contacts

Individual messages by phone, email, web chat, social media, or other mechanism.

Erlang (staffing calculation method)

A staffing calculation method that determines the number of agents needed to handle a forecast volume of inbound calls. It is named after the Danish statistician who invented it. There is a family of Erlang methods but Erlang-C is most commonly used in contact centers. Erlang-C takes into account the expected volume of calls, the expected average handling time and the desired service level. See also 'staffing calculation'.

Forecasting

The process of predicting future contact metrics such as the number of offered calls and average handling time (AHT) using historical data and the business intelligence that you add, such as upcoming marketing campaigns. See also 'staffing calculation'.

Full-time employee

An employee, e.g. an agent, whose working hours are 'full time'. The definition of 'full time' varies by region and company. For example, in the United States a full-time employee typically works 40 hours per week.

Full-time equivalent (FTE)

A staffing arrangement equivalent to one person working full time. For example, if full-time is defined as 40 hours per week, two employees each working 20 hours per week contribute one FTE towards the number of required staff.

Inbound contacts

Contacts, e.g. phone calls, which are initiated by individuals outside the contact center, e.g. customers, at a time of that individual's choosing.

Interval

The window of time within which historic data are aggregated and within which performance is evaluated. Historic data is typically collected in 15, 30, or 60-minute intervals. Forecasts are generated down to the same intervals and KPIs such as coverage and service level are also evaluated at these intervals.

Occupancy

The percentage of an agent’s logged-in time that is spent on contact-related activity, including talk time, hold time, and after-call work (ACW). For example, if a contact center has an occupancy rate of 75%, it means that its agents are spending three-quarters of their logged-in time performing contact-related activities. Good practice is not to exceed 90% occupancy, to avoid agent burnout.

Offered calls

Calls that arrived in the contact center but were not necessarily answered. Offered calls include answered calls and abandoned calls. Offered calls are the preferred input for forecasting, since the goal is to schedule sufficient staff that offered calls are answered within the service level target.

Optimized scheduling

A scheduling method that aims to consistently minimize under- and over-staffing by matching the number of scheduled agents with the number of agents required, as closely as possible. Optimized scheduling enables the consistent achievement of service level goals, while also minimizing employment costs and avoiding agent stress and burnout. To build a viable schedule, planners need to take into consideration all the relevant constraints, such as working times specified in agents’ employment contracts.

Part-time employee

An employee, e.g. an agent, whose working hours are less than 'full time'. See also 'full-time employee'.

Rostering

The process of creating schedules for employees without regard for the underlying staffing demand. Contrast with scheduling.

Scheduling

The process of creating schedules for agents with the goal of matching the 'supply' of agents with 'demand' for agents. Contrast with rostering.

Service level

A measure of the speed with which contacts are responded to, typically expressed as the percentage of contacts answered within a given time. Many call centers adopt an 80/20 service level. This means that the goal is to answer 80% of calls within 20 seconds. The target service level has a significant impact on the number of employees required to deliver the service. See also 'staffing calculation'.

Staffing calculation

A mathematical formula or algorithm which determines the number of agents needed to handle a forecast number of offered contacts. Different contact channels require different staffing calculation methods. Erlang-C is a method commonly used to calculate staffing for inbound calls. Web chats require a staffing calculation method that factors in concurrency. Emails and other asynchronous contacts require a linear staffing calculation method that translates volume and AHT into a required headcount over a period of hours. Outbound contacts require a calculation which takes into account the size of the campaign and properties such as right party connect rate. Multi-skill scheduling requires a special approach to staffing calculation and each WFM vendor offers a distinctive solution for this.

Talk time

The amount of time during a call or other contact when the agent and customer are in conversation. Waiting time, hold time and after-call work are not included.

Volume of calls or contacts

The number of incoming calls or other contacts, typically measured in intervals of 15 or 30 minutes. In forecasting, the volume of contacts is a function of total volume over a period, e.g. one week, and the pattern of contacts which is calculated at intervals, e.g. 15 minutes.

Volume of calls or contacts

The number of incoming calls or other contacts, typically measured in intervals of 15 or 30 minutes. In forecasting, the volume of contacts is a function of total volume over a period, e.g. one week, and the pattern of contacts which is calculated at intervals, e.g. 15 minutes.

Workforce management (WFM)

A discipline and a category of sofware application that helps put the right number of people with the right skills in place at the right time to handle an accurately forecast workload to a defined service level.

Workload

The headcount required to process a given volume of contacts. Typically the result of a staffing calculation.