Inbound Call Center Staffing Models: Right-Sizing Your Team for Seasonal Demand

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Inbound call center staffing models are approaches to determine how many agents you need, with what skills, and across which shifts. These different staffing techniques combine forecasting, capacity planning, scheduling, shrinkage adjustment, and real-time intraday management. Usually, Erlang C staffing formulas and modern workforce management (WFM) tools are used to determine the “right” internal headcount.

As a VP or director of a growing D2C company, assume that there are two businesses receiving the same number of customer calls. 

• One answers almost every call on time, while the other struggles with long wait times, abandoned calls, and overworked agents. 

Is the difference in service quality due to the size of the team? Nope! It is the staffing model and call center workforce planning behind the operation. The “right” inbound call center staffing model helps businesses decide how many agents they need, when they need them, and which enquiries each agent should handle. 

Read this article to learn about the different inbound call center staffing models and how the Erlang C staffing formula estimates staffing requirements.

4 Core Components of an Inbound Call Center Staffing Model

An inbound call center staffing model helps you decide how many customer support agents you need and when you need them. It is based on four key parts:

1. Forecasting

Forecasting means estimating how many customer calls, chats, or emails your business is likely to receive during different times of the day. Instead of predicting the total number for the whole day, businesses usually estimate demand in short time blocks, such as every 30 minutes.

These estimates are based on:

• Past customer contact data
• Seasonal trends (such as holiday periods)
• Marketing campaigns that may increase customer enquiries
• Product launches, sales events, or other business activities

Accurate forecasts allow D2C companies and consumer brands to prepare the right number of agents before customer demand increases.

2. Scheduling

Scheduling means creating work shifts for agents based on the forecast. The goal is to:

• Have enough agents available when customer enquiries are expected to be high 

and

• Avoid having too many agents when demand is low

Scheduling also considers the mix of agents required, such as experienced agents for complex issues and newer agents for routine enquiries. A good schedule helps maintain service levels while avoiding unnecessary staffing costs.

3. Intraday Management

Even the best forecast may not match actual customer demand. “Intraday management” means monitoring customer contact volume throughout the day and making changes whenever needed. For example, if more customers contact your business than expected, managers may:

• Ask backup agents to log in
• Reschedule agent breaks
• Move agents from low-priority tasks to customer support

While doing call center workforce planning, these adjustments help maintain service quality when demand changes unexpectedly.

4. Shrinkage Management

As a VP or senior manager of a D2C company, realize that NOT every paid hour is spent handling customer enquiries. “Shrinkage” refers to the time when agents are unavailable for customer interactions because they are:

• Taking breaks
• Attending training sessions
• Participating in team meetings
• On paid leave
• Absent from work

In many contact centres, shrinkage ranges from 20% to 35%, although the actual percentage depends on company policies, labour laws, and the location of the business. Growing DTC companies, consumer brands, and other small businesses must include shrinkage while planning staffing requirements. Otherwise, there may not be enough agents available to handle customer enquiries.

How Do These Four Components Work Together?

In an inbound call center staffing model, the four components mentioned above operate as follows:

• Forecasting estimates customer demand. 
• Scheduling creates agent shifts to match that demand. 
• Intraday management handles unexpected changes during the day. 
• Shrinkage management accounts for the time when agents are unavailable.

Together, these inputs are used in a capacity planning process, which calculates the number of Full-Time Equivalents (FTEs) required for each time interval. For those unaware, an FTE represents the workload of one full-time employee. This helps businesses determine how many agents are needed to meet customer demand throughout the day.

What is the Erlang C Staffing Formula?

Many businesses use the Erlang C staffing formula to estimate how many customer support agents they need for inbound calls. The formula helps answer a simple question:

• “How many agents should be available so that customers do not wait too long for their calls to be answered?”

For example, suppose a business wants 80% of customer calls to be answered within 20 seconds. Now, Erlang C staffing formula estimates the minimum number of agents required to achieve that target.

What are the Various Inputs Used in the Erlang C Staffing Formula?

The formula uses several inputs to calculate staffing requirements. Let’s check them out:

1. Call Volume (λ)

Call volume is the estimated number of incoming calls during a specific time period, such as every 30 minutes or every hour. For example, 

• If you expect 300 calls between 10:00 AM and 11:00 AM, the Erlang C staffing formula uses that number while calculating the required staffing level.

2. Average Handle Time (AHT)

Average Handle Time (AHT) is the average time an agent spends on one customer interaction.

It includes:

• Talking to the customer

and

• Time spent after the call to update records or complete any required work

For example, if an average customer interaction takes six minutes from start to finish, the AHT is six minutes.

3. Target Service Level (SL)

The service level is the customer service goal that the business wants to achieve. A common target is 80/20, which means 80% of incoming calls should be answered within 20 seconds.

D2C companies and consumer brands with higher customer service expectations may set more demanding service level targets.

4. Occupancy Target

Occupancy measures how much of an agent’s working time is spent handling customer interactions. For example:

• Suppose an agent spends 48 minutes handling customer calls during one working hour.
• In this case, the occupancy rate is 80%.

When developing a flexible inbound staffing strategy, most contact centres aim for an occupancy level of 80% to 85%.

What Does the Erlang C Staffing Formula Calculate?

After analysing the above inputs, the Erlang C formula estimates the minimum number of agents required during each time interval to achieve the target service level. This gives businesses a starting point for workforce planning. To understand better, let’s study a hypothetical example:

Example: How the Erlang C Formula Works in a U.S. Contact Center

Suppose a U.S. retail company’s customer support centre expects 600 customer calls between 9:00 AM and 10:00 AM during its holiday shopping season. Here are the inputs:

• Expected calls: 600
• Average Handle Time (AHT): 5 minutes per call
• Target service level: 80% of calls answered within 20 seconds (80/20)
• Target occupancy: 85%

The Erlang C staffing formula uses these inputs to estimate the number of agents needed.

The formula may calculate that about 60 agents must be available between 9:00 AM and 10:00 AM to answer 80% of calls within 20 seconds. However, this is not the final staffing requirement.

If the company expects 25% shrinkage due to breaks, meetings, training, and leave, it cannot schedule only 60 agents. In this case, the staffing calculation becomes:

• Agents required to handle calls: 60
• Shrinkage: 25%
• Total agents to schedule: 80

This means that although 80 agents are scheduled, only around 60 agents are available to handle customer calls at any given time. Through this example, you can observe how the Erlang C staffing formula provides the minimum number of agents needed to meet the service target, while businesses add shrinkage and other adjustments before finalising staffing levels.

5 Major Types of Inbound Call Center Staffing Models 2026

Every business receives different types of customer enquiries. Some businesses handle only one type of request, while others receive enquiries related to sales, billing, technical support, returns, or account management. 

Due to these differences, businesses use different inbound call center staffing models to organise their customer support teams. The “right” staffing model helps managers assign agents based on the type of customer enquiries they receive. It also supports better workforce planning and improves customer service. 

For more clarity, let’s check out the five types of most common inbound call center staffing models:

1. Single-Skill, Single-Queue Model

A Single-Skill, Single-Queue Model is the simplest type of inbound call center staffing model. In this approach, every customer enquiry goes into one common queue, and every agent is trained to handle the same type of enquiry. Since all agents have the same skills, any available agent can answer the next customer interaction.

This inbound call center staffing model is suitable for businesses that offer a limited number of products or services and receive similar customer enquiries throughout the day. Additionally, some more advantages offered by this model are:

• Simple to manage because there is only one customer queue.
• Workforce planning is easier because all agents perform the same role.
• Scheduling is straightforward since any agent can cover any shift.
• Businesses can use standard staffing methods, such as the Erlang C staffing formula, to estimate staffing requirements.

However, this model also has limitations. If customer enquiries become more specialised, not every agent may have the knowledge to solve every issue. Therefore, as a D2C business grows and launches new products or adds specialised services, this staffing model may become less suitable due to customer enquiries becoming more diverse.

2. Multi-Skill, Multiple-Queue Model

A Multi-Skill, Multiple-Queue Model is designed for businesses that receive different types of customer enquiries requiring different expertise. Instead of placing every customer into one common queue, enquiries are divided into separate queues based on the issue. Next, agents are trained for specific skills, and calls are routed to the most suitable agent.

For example, consider a U.S. software company that provides cloud-based accounting software. Customers may contact the company for different reasons, such as:

• Sales enquiries from potential customers
• Technical support for software issues
• Billing and subscription questions

Following this inbound call center staffing model, the company may organise its team like this:

• Bob handles only sales enquiries.

• John handles only technical support.
• Mary is trained in both sales and technical support.

The advantage? When a customer calls about billing, the system routes the call to a billing specialist. If another customer wants a product demonstration, the call goes to a sales agent. If technical support receives a sudden increase in calls, Mary can also assist because she has both skills.

This inbound call center staffing model offers several benefits:

• Customers are connected to agents with the right expertise.
• More customer issues are resolved during the first interaction, improving First Call Resolution (FCR).
• Businesses can provide specialised support for different products, services, or departments.

However, this model is more difficult to manage than a single-queue model. Each skill group receives different numbers of enquiries throughout the day. As a result, one team may become overloaded while another has fewer customer interactions. 

3. Tiered (Escalation) Model

The Tiered (Escalation) Model divides customer support into different levels based on the complexity of the customer’s issue. Instead of having every agent handle every enquiry, businesses assign different responsibilities to different teams. As per general industry understanding, this inbound call center staffing model works like this:

For example, consider a U.S. bank. A customer calls to check the balance of their savings account. A Tier 1 agent can answer this request. Another customer reports an unauthorised transaction on their credit card. Since this issue requires investigation, the call is transferred to a Tier 2 specialist.

This inbound call center staffing model offers several advantages:

• Routine enquiries are handled by general support agents.
• Specialists spend their time on complex customer issues.
• Businesses can reduce staffing costs because highly skilled specialists are needed only for advanced cases.
• In many contact centres, Tier 1 agents resolve around 70% to 80% of all customer enquiries, leaving only complex cases for higher support levels.

However, this model also has limitations. If Tier 1 agents cannot resolve an issue, customers must explain the problem again after the call is transferred. Frequent escalations can increase customer frustration and extend the overall resolution time.

4. Hybrid (Onshore + Offshore) Model

The Hybrid (Onshore + Offshore) Model combines customer support teams located in different countries. In this inbound call center staffing model:

• The onshore team operates in the same country as the business and handles sensitive or high-value customer interactions.
• The offshore team operates from another country and manages routine customer enquiries, overflow calls, or after-hours support.

For example, a U.S.-based insurance company may keep a support team in the United States for policy disputes, legal matters, and premium-related enquiries. At the same time, it may partner with a contact centre in India or the Philippines to handle policy information, claim status updates, and general customer questions.

This inbound call center staffing model offers several benefits:

• Businesses can reduce labour costs because offshore staffing is often less expensive.
• Support capacity can be increased without expanding the onshore workforce.
• Customers can receive support outside regular business hours through teams working in different time zones.
• Onshore specialists can spend more time handling complex customer issues.

Despite these advantages, businesses must manage several operational challenges.

Customer service quality should remain consistent across both teams. Training materials, operating procedures, and service standards must be the same for onshore and offshore agents. Also, businesses must maintain strong communication between teams, and do careful scheduling because employees may work in different time zones.

5. Gig or On-Demand Staffing Model

The Gig or On-Demand Staffing Model uses a “flexible workforce” that expands or contracts based on customer demand. Instead of employing the same number of agents throughout the year, businesses add temporary or freelance customer support agents during busy periods and reduce staffing when demand falls.

This inbound call center staffing model is more useful for seasonal staffing call centers where customer enquiries change significantly throughout the year. For example, 

• Suppose an e-commerce company may receive three times its normal customer enquiries during Black Friday or the holiday shopping season. 
• Rather than hiring permanent employees for the entire year, the company brings in additional remote agents for a few weeks to handle the increased workload. 
• Once customer demand returns to normal, the temporary workforce is reduced.

This model provides several advantages:

• Staffing costs remain lower during periods of low customer demand.
• Businesses can increase support capacity during seasonal peaks or major product launches.
• Remote agents can be recruited from different locations, giving businesses access to a larger talent pool.
• Businesses avoid maintaining a large permanent workforce when it is not required.

However, this model also presents challenges. Temporary agents may have limited knowledge of the company’s products, systems, or customer service processes. Also, since gig workers may not stay with the company for long periods, businesses also need ongoing recruitment and training to replace agents who leave. 

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So now you know about the various inbound call center staffing models and the Erlang C staffing formula used for workforce planning. To recap, businesses use different staffing models based on the type of customer enquiries they receive, the size of their support team, and their operational requirements.

As per general industry understanding, some commonly used models are:

• Single-Skill, Single-Queue Model: All agents handle the same type of enquiry from one common queue.
• Multi-Skill, Multiple-Queue Model: Agents specialise in different enquiry types, and calls are routed based on their skills.
• Tiered (Escalation) Model: Routine enquiries are handled by Tier 1 agents, while complex cases move to specialist teams.
• Hybrid (Onshore + Offshore) Model: Customer support is shared between local and offshore teams.
• Gig or On-Demand Staffing Model: Temporary or remote agents are added during periods of high demand.

The Erlang C staffing formula complements these models by estimating the minimum number of agents required to meet a target service level. Businesses then adjust the result for factors such as shrinkage, AI-assisted support, and multichannel operations before finalising staffing requirements.

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Inbound Call Center Staffing Model FAQs

1. Which inbound call center staffing model is best for a small business?

If your team handles similar customer enquiries, a Single-Skill, Single-Queue Model is usually the best choice. It is easier to manage, requires less workforce planning, and works well when every agent can handle the same type of customer request.

2. Is the Erlang C staffing formula suitable for every business?

The Erlang C staffing formula could be a good starting point only for estimating staffing requirements. The result derived from this formula should also account for factors such as breaks, leave, AI automation, chat support, and agents with different skill sets before making staffing decisions.

3. Which metrics should I monitor to know if my staffing model is working in 2026?

You may track key metrics such as Service Level (SL), Average Speed of Answer (ASA), Occupancy Rate, First Call Resolution (FCR), Abandonment Rate, Shrinkage, and Cost Per Contact. 

These metrics show whether your team size matches customer demand and whether staffing changes are needed.