Grade of Service

The Grade of Service metric (or GOS for short and also known as Service Levels) is the old workhorse of call centre KPIs and one of the most common metrics you will find.

In simple terms, Grade of Service refers to the percentage of calls answered within a given time frame.

Most commonly, you will see or hear it as two numbers like 80/30 meaning a GOS target of 80% of calls answered in 30 seconds.

There is a direct correlation between your Grade of Service (aka Service Levels) targets and the amount of staff you need:

  • Where you have high GOS targets where a high percentage of calls must be answered (e.g. 90% of calls answered in 10 seconds) you will need more staff.
  • Where you have low GOS targets like answering 70% of calls in 60 seconds you need less staff

Determining the exact number of staff you need to achieve a particular Grade of Service target can be calculated using an Erlang C Calculator.

What is the industry average Grade of Service target for call centres?

You will often hear 80/30 (so 80% of calls answered within 30 seconds) mentioned however there really is no industry standard.

The targets you set must be aligned with your business objectives by asking one simple question:

How critical is it for your business if customers have to wait?

In an emergency services setting, they have Service Level targets as high as 100/5 (100% of all calls must be answered within 5 seconds) whereby in the public service, where perhaps there is no alternative for the customers, Grade of Service targets can be more like 70% in 30 minutes. Ouch.

In a revenue-generating centre where every call can result in a sale, it makes commercial sense to have a high Grade of Service target so you don’t lose sales.

In service, it’s not as overwhelmingly obvious however nearly every study on customer experience suggests that when customers don’t like the service you provide, they will go elsewhere.

Ultimately, the right Grade of Service target for your business needs to weigh up a range of factors including customer expectations, budgets and more.



Is there any industry data on GOS?

As I mentioned above, the most important benchmark is your customer’s tolerances for waiting but if you’d like to know what everyone else is doing, the most recent Australian survey that specifically contained data on Grade of Service was back in Jan 2018 by a company called Fifth Quadrant.

The most common Service Level targets were:

  • 80% of calls answered in 20 seconds (22%)
  • 80% of calls answered in 30 seconds (15%)
  • 90% of calls answered in 10 seconds (8%)
  • 90% of calls answered in 30 seconds (6%)
  • 70% of calls answered in 30 seconds (7%)

There is also more recent industry data available from the 2020/21 Contact Centre Industry Best Practice Report >

How do you calculate the resources you need to achieve a Grade of Service?

It’s actually not that hard if you have the right tools!

Thankfully we have an Erlang C Calculator that will tell you exactly how many resources you need to achieve a certain level of Grade of Service.

We’ve written the instructions so it’s easy to follow along and model the impact of changing your Grade of Service targets so you can see how many less or more staff (and therefore cost) you need if you change your targets.

Just remember though, one of the contact centre fundamental principles is that the higher the Service Levels you want to achieve, the more resources you will need.

Get the free calculator >>



Risks of using Grade of Service Targets?

The key missing element from the GOS Metric though is it doesn’t tell you what happens to the customers that don’t achieve the GOS metric.

So if the target is 80/30 we know that 80% of calls were answered within 30 seconds.

But what happened to the other 20%?

Did they wait an average of 50 seconds, 5 minutes or two hours?

GOS conveniently doesn’t tell us this which is why its a very dangerous metric to use on its own…

GOS Service Levels Definition
GOS doesn’t tell you what happened to the customers who didn’t get answered within the defined percentage.


The other thing to be wary of with GOS is how often it’s measured.

Is it an average over a whole month, a day, or even an hour?

All come with various pros and cons so it pays to be very clear on the frequency of measurement.

So next time the boss asks “what’s the GOS?” you now know the right answer to give 😉

Recommended further reading: The truth about the call centre abandonment rate metric

Where can I learn more about Grade of Service?

Our aim is to help you learn more about Grade of Service (and contact centres in general) in the style that suits you best:

Watch the video

Connect with Justin Tippett on LinkedIn >