Agent Motivation

Call Center Staffing: How Many Agents Do You Need?

For growing companies with ambitious customer service goals and limited resources, call center staffing can be tricky. What’s the magic number of call center agents you need for a team just big enough to meet demand and serve customers well?

Calculating call center staffing levels isn’t as simple as dividing the number of call minutes per day by hours in the day. There’s much more you need to account for to get the number right. Once you have the right inputs, and plug them into the right formula, you’ve already won half the battle.

All that’s left to do is conquer call center attrition so you can stop scrambling to backfill vacancies while trying to build out your team.

Here are some best practices that will help you succeed on both fronts.

The Erlang C Formula: Balancing Customer Service Goals with Call Center Staffing Costs

Erlang C is a standard formula for determining the number of call center agents are needed based on call volumes, Average Handle Time (AHT), and customer service goals. But using an Erlang calculator isn’t as easy as it looks.


Call center erlang calculator helps your calculate call center staffing needs


If you plug in the wrong numbers—for example, an impossibly high 100% for max occupancy, or agent productivity—you’ll either drive up call center costs with no appreciable return, or you’ll end up with too few agents and a lower quality service experience.

The process of determining the number of incoming contacts during a given time period is fairly straightforward, but calculating Average Handling Time (AHT) is a bit trickier.


(Total talk time + total hold time + total wrap-up time)

Number of calls handled

There are
several factors that can distort your AHT calculation, such as the inclusion of shrinkage time (i.e., the time agents spend on break or in meetings). Also, handle times can vary by day part and by day of the week. For the sake of accuracy, you need to account for these distinctions and variations.

A final word of caution: it might be tempting to focus on reducing AHT in the call center to minimize call center staffing levels, but this will negatively impact service quality in other ways. If agents are pushed to end calls as quickly as possible, they will—at the expense of first contact resolution  (FCR), nurturing the customer relationship, and driving current and future sales.  

What Are Your Customer Service Goals?

For the Erlang calculator, you’ll need to set a goal for maximum hold time and the minimum percentage of calls that must be answered within that time frame. Using the example above, 80% of calls answered within 20 seconds would require 17 agents. A more ambitious goal of 90% of calls answered within 10 seconds would require just two additional agents.

The Erlang C predictions in this chart, based on a 20-hour workload, show how slight variations in front-line call center staffing totals can dramatically impact service quality. Scaling the team from 21 to 24 agents, for example, eliminates more than half of delayed calls and cuts the customer’s wait time by 75%.

number of call center staff matrix

How ambitious should your service goals be? We can’t answer that for you. But we do know that a fast phone or chat response is one of the most important aspects of the customer service experience. It not only helps to create effortless customer experiences (which lead to higher repurchase rates and customer spend), but also reduces call center costs. The longer the wait time, the likelier customers are to end the call or chat and reach out through another brand channel. This is why Average Patience (average time to abandon, or ATA) is an integral part of the Erlang calculation.

In our studies of the StellaService Ecommerce Index—30 leading ecommerce retailers from Amazon to Zappos—we’ve found that our Index brands have clearly stepped up their investment year over year to increase their response times. From a competitive standpoint, and for the sake of efficiency in a multichannel environment, minimizing your customers’ wait should be a top priority, and call center staffing is a key way to help with this.

Contact Center Attrition: The Biggest Cost Driver of All

Scaling a customer service team is complicated enough. Doing so while attrition remains high is like taking one step forward and two steps back. Each new vacancy brings additional hiring and onboarding costs as well as the ramp up to full productivity and lost sales opportunities.

If you’re serious about balancing service quality and operational costs as you grow, and optimizing both along the way, you can’t simply account for high turnover. You need to defeat it by focusing on hiring the right people and keeping them on your team.


More important than skills and experience are the qualities that will make new agents comfortable and successful on the job. Look for career-minded people who are a good fit for the brand’s culture and values. Better yet, look for people who share the qualities of your top-performing agents. We recommend using front-line customer data to create agent “personas” to help inform your hiring decisions.

Performance Management

A relevant, robust performance management program gives agents the skills and confidence to excel, motivates them to improve, and helps them advance their careers. A program that relies on sparse data, internal quality measures, and subjective assessments can have the opposite effect.

What separates these two types of programs are the data that drive them. Using real-time customer feedback from the front line—for micro-coaching, customer-driven customer service training, and more meaningful QA reviews—can transform the contact center’s culture and operations and its value to the brand.

Motivation and Engagement

Customer service agents need to feel connected and supported, and they need to believe in what they’re doing. From on-the-spot encouragement and praise to recognition and rewards, there are many tools you can use to motivate your team—as long as they’re meaningful from the agent’s point of view.

Companies like ezCater, Lane Bryant, and Brooklinen are as invested in their people as they are in creating loyal customers. They know that loyal, engaged front-line employees are their greatest assets. As a result, these companies enjoy the dual rewards of high retention and highly satisfied customers—with increasing benefits for the top and bottom line.

If you are looking to scale your team and want to monitor the performance of your agents – make sure to check out Stella Connect.