• Clive Woodrow

Calculate Service Level Correctly

Updated: Mar 1, 2020

Many of my post ideas come from working with different clients and seeing the challenges they face in their business.

In this post, I want to talk about how to calculate the service level in your contact centre. Which is probably the most important measure of success from a customer’s perspective.

First off, let's define what service level is. In our case, the service level objective is 80% of our calls are answered within 20 seconds.

When I ask my clients team what their service level was for the week, I received the following.

I asked them how did they calculate it, and they provided me with this formula.

Mathematically the number is correct. But it was also very wrong. And here's why

For any contact centre that operates 7 days a week, there is inevitably heavier call volume in particular days.

As you can see here, the centre took over 20,000 calls in the week with a good measure of the volume happening on Monday, Tuesday and Wednesday. The first three days of the week represented over 12,000 calls or 60% of the week's volume, and in each of those days, you notice the service level was significantly below our goal of 80 in 20 and what the teams calculated weekly average of 78.0%.

I find that if you visualize the call volume in the form of a bar chart, you can see the dramatic changes in volume day over day. You can make that chart even more compelling if you overlay the daily service level, as we have done in the picture above.

The green represents the calls that were answered within the service level objective. The yellow represents all the other calls answered outside of that.

You can see the impact the high call volume had on the service level at the beginning of the week.

In this chart, we used the service-level average the team calculated earlier.

Yes, it's unfair to have each day at 78% service level. I do that to compare the amount of yellow in the Actual Service Level chart to the Weekly Average Service Level chart.

As you back and forth between the two charts, I think you would agree that our Actual Service Level chart has more yellow in it then our Weekly Average Service Level chart.

So without knowing any math, you can pretty much assure yourself that the average might be a little bit hight.

Let's do the math and find out what the weighted average service level was for the week.

Weighted average means - in the data we are using, some days carry more importance than others.

This is how you calculate your Weighted Average service level.

First, we calculate the weighted volume for any one particular day. This is simply the total of the days call volume divided by the total volume for the week and expressed as a percentage.

Then you take that number and multiply it by the service level for that day. The result is the weighted daily service-level. Monday's weighted service level was 11.1%, Tuesday 13.1%, and so on.

All of the weighted service levels are added together to give you the total weighted average service level for the week. When we add all those up, we get 71.8%.

The team's original calculation of 78.0%, which was 6.2 % higher. So, in essence, they were going to report a service-level that was actually better than it really was.

It is very important to report accurate numbers. There could be significant impacts on business agreements, contracts, investments and bonuses should these types of numbers be calculated incorrectly.

In our example, the service level decreased, but I'm happy to report that I've seen many examples where the service level was better than what was reported.

Thank you for reading, If you would like the PDF of this presentation that includes additional bonus slides that show each step of the calculation, then please email me at the following:

You can find other useful call centre management information at:

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