What is Service Level?

Service level, in a contact center, is the percentage of incoming contacts answered within a defined target time. It is most often written as a paired number such as 80/20, meaning “answer 80% of contacts within 20 seconds.” Service level is the headline measure of how quickly a center responds to customers, and it is the target that workforce management staffs against. It is closely related to — but not the same as — a contractual Service Level Agreement (SLA).

How service level is calculated

The common formula divides the contacts answered within the threshold by the total contacts offered, over a measurement interval:

Service level = (contacts answered within target time ÷ total contacts offered) × 100

The two parameters define the goal:

• The percentage — what share of contacts must be answered in time (e.g., 80%).
• The threshold — the time window that counts as “answered promptly” (e.g., 20 seconds).

How abandoned calls are treated changes the result. Different formulas include or exclude calls abandoned before the threshold, so two centers quoting “80/20” can be measuring slightly differently — it is worth defining the method explicitly.

Service level vs. SLA vs. ASA

These get used interchangeably but mean different things:

• Service level — the operational metric (percent answered within X seconds).
• SLA (Service Level Agreement) — a contract that commits to a service-level target and often penalties for missing it. The metric is what you measure; the SLA is what you promise.
• Average speed of answer (ASA) — the average wait before answer. ASA and service level are related but not identical: a low ASA can still hide a tail of long waits that a service-level target exposes.

Why service level matters

Service level is the clearest proxy for accessibility: can customers reach you quickly? Miss the target and queues lengthen, abandonment rises, and satisfaction (CSAT) falls. Beat it by too much and you are likely overstaffed, paying for idle agents. The art is staffing precisely to hit the target — the core job of workforce management, which uses volume forecasts and average handle time from the ACD to compute the agents needed per interval.

Common service-level targets

• 80/20 — answer 80% within 20 seconds, a widely used general benchmark.
• 90/15 or 90/30 — tighter targets for premium or sales lines.
• Targets vary by industry, channel, and cost tolerance; there is no single universal “correct” number.

Service level frequently asked questions

What does 80/20 service level mean?

It means answering 80% of incoming contacts within 20 seconds. The first number is the percentage of contacts to answer promptly; the second is the time threshold that counts as prompt. It is a common general benchmark, not a universal rule — targets vary by industry and channel.

What is the difference between service level and an SLA?

Service level is the operational metric — the percentage of contacts answered within a target time. An SLA (Service Level Agreement) is a contract that commits to achieving a service-level target, often with penalties for missing it. The metric is measured; the SLA is promised.

How is service level calculated?

Divide the number of contacts answered within the target time by the total contacts offered in the interval, then multiply by 100. The definition of the threshold and how abandoned calls are counted affect the result, so the measurement method should be stated explicitly.

What is the difference between service level and ASA?

Service level is the percentage answered within a set time; average speed of answer (ASA) is the average wait time before answering. A good ASA can still conceal some very long waits, which a service-level target with a hard threshold makes visible. Many centers track both.

See how DialPhone reports service level

DialPhone’s contact center tracks service level, average speed of answer, and abandonment in real time, giving supervisors the live view they need to hit targets and the historical data workforce management uses to staff accurately.