Interval (WFM)

What is an Interval in Workforce Management?

An interval, in workforce management, is the fixed block of time, commonly 15 or 30 minutes, into which a day is divided for forecasting call volume and scheduling agents. Rather than forecasting or staffing for an entire 8-hour shift as one lump, WFM systems break the day into these smaller intervals so staffing can flex to match demand that rises and falls throughout the day.

Why granularity matters here

Call volume in most contact centers isn’t remotely flat across a day; it typically spikes around specific hours, such as right after a business opens or during a lunch break window, and drops during quieter periods. Forecasting and scheduling at a daily or even hourly level would smooth over those spikes, leading to overstaffing during quiet intervals and understaffing during busy ones. Shorter intervals, like 15 or 30 minutes, let a WFM system match staffing far more precisely to when calls actually arrive.

How intervals are used in practice

• Forecasting: historical volume is broken down by interval to predict how many contacts will arrive in each 15 or 30-minute block.
• Staffing calculations: models like the Erlang C formula calculate the number of agents needed per interval to hit a target service level.
• Real-time monitoring: supervisors compare actual volume against the interval forecast throughout the day to catch and correct deviations early.

Choosing an interval length

Shorter intervals give more precise staffing but require more granular, reliable historical data to forecast accurately, and can make schedules harder for agents to follow if breaks and shift changes get too fragmented. Most contact centers settle on 15 or 30-minute intervals as the practical balance between precision and manageability, though this can vary by call volume and business type.