If you have ever worked in or managed a call center, you have probably heard the term “service level”. But what does it actually mean? And why do so many managers focus on it?

In the simplest terms:
Service level is the percentage of incoming calls answered within a specific time frame.

For example, if your target is 80/20, that means you aim to answer 80% of calls within 20 seconds. It sounds simple, but this one metric can influence your staffing plan, your budget, and your customers’ experience.

Why Service Level Matters

Think of service level as the pulse of your customer support operation. It shows whether customers are getting help quickly or being left waiting.

• Customer Experience: Long wait times frustrate customers and increase the chance they will hang up or leave with a negative impression.

• Staffing Accuracy: Too few agents and your service level drops. Too many agents and you are paying for idle time.

• Business Reputation: Many industries, from utilities to tech support, use service level agreements (SLAs) as a competitive benchmark.

The Standard: 80/20 (And Why It Is Not Always Right)

You might hear people talk about the 80/20 rule like it is a universal law. While it is common, it is not the only standard. Some businesses target 90/15 for a more premium experience. Others accept 70/30 if budgets are tight or call urgency is low.

Here is the catch:
Higher service levels require more staff. That 10% improvement from 80% to 90% can mean a significant staffing increase and cost.

How Service Level Is Calculated

There are really two parts to calculating service level, and both are important.

1. Setting Your Target Service Level

Before you run any numbers, you decide what your goal will be. This is based on the type of customer experience you want to provide, your budget, and the nature of your calls.

• A common standard is 80/20 (answer 80% of calls within 20 seconds) because it balances speed with staffing costs.

• Higher targets like 90/15 provide a faster, premium experience but require more agents.

• Lower targets like 70/30 can work if budgets are tight or calls are less urgent.

It is important to remember that hitting an 80/20 target does not mean every caller gets answered in under 20 seconds. It simply means that 80% do. The remaining 20% could wait significantly longer, and those longer waits will push your Average Speed of Answer (ASA) higher than the target.

At Spark Queue, we get this question often: “Why is my projected ASA higher than my service level target?”
The answer is that ASA is an average of all answered calls, not just the ones that met the target. So if a portion of calls wait much longer, that average increases — even if you are meeting your service level goal.

2. Measuring Your Actual Service Level

Once your target is set, you track how well you are hitting it using this formula:

(Number of calls answered within target time ÷ Total calls answered) × 100

For example, if you receive 1,000 calls in a day and 800 are answered within 20 seconds, your service level is:

(800 ÷ 1,000) × 100 = 80

This number shows you how you are performing against your goal so you can make informed staffing and process adjustments.

The Staffing Connection

Here is where service level becomes more than just a number. Your staffing forecast is built around achieving that target. This is where the Erlang C formula comes in, a calculation used by workforce management (WFM) teams to determine how many agents you need based on:

• Call volume

• Average handle time (AHT)

• Target service level

• Shrinkage (time not spent on calls)

• Occupancy

Even small changes in your service level target can cause big shifts in your staffing requirements.

For those who want truly accurate staffing without wrestling with unreliable spreadsheets or formulas, Spark Queue applies this logic intelligently so you can see exactly how your service level impacts your agent needs.

Making Service Level Work for You

Service level should not just be a “check the box” metric. It is a decision-making tool:

• Use it to justify staffing changes

• Track it alongside abandon rate and FCR to get the full picture

• Adjust it for different channels such as phone, email, and chat

How Spark Queue Helps

Most "lean" contact centers do not have the time or the formulas to figure out exactly how service level impacts their staffing. Additionally, the tools that are out there are typically bloated and incredibly expensive. Spark Queue is shaking up the industry and finally fixing that.

Spark Queue does the heavy lifting for you:

• Plug in your service level target and see how it changes your agent requirements instantly

• Compare “what if” scenarios to balance customer experience and cost

• Build a realistic staffing plan that works in the real world

When you understand and control your service level, you control your customer experience.