Calls Answered within SLA - Calculation

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Support Specialist

We have an SLA of 80% of calls to be answered in 60 seconds.

This is great but there seems to be a dispute on how to calculate this.

Some say that the calculation should be only on calls answered as the abandoned calculation is separate.

E.g. Calls answered in 60 seconds divided by total calls a percentage.

Other say that the abandons should be factored in as they too have not been answered.

E.g. Calls answered in 60 seconds divided by total calls offered a percentage.

Is there an industry standard on this type of calculation for a Help Desk where the calculation only starts once a specific queue/option has been selected?


Able Consulting Solutions

Hi Peter,

I would include your abandoned calls; if you don't then it will inflate your SLA calculation, from a customer experience point of view the customers have still had to wait to get answered.

The fact that there expectation is that the call should have been taken quicker therefore they hung up should not be dismissed from the SLA.

Still have a target of say less than 5% abandonment rate.

It may also depend on your commercial set-up i.e. you supply third party support for clients many challenges can be hidden in calculations!!

Hope that helps


Support Specialist

Hello Neil,

Thank you for the quick responce,

I agree with you and have been doing my calculatins in that manner, however I am picking up more and more flack from the management when they are on the boarder line.

Is there a way to better explain or convince?


Hi PeterPan,

I would say that it depends on how strict you want to be to your service level. There are more than two ways of calculation.

If I am not mistaken, ICMI recommends to use the following calculation:

(calls answered + calls abondoned) in X sec divided by (total amount of calls answered + calls abondoned).

The two calculations you have mentioned would give the highest and lowest Service Level. While the one I have mentioned would be somewhere in between.

Call Centre Manager

The Private Clinic

Peter Pan

We work on the following,

A) less than 5% Abandon Rate (ignore all calls abandoned within 4 sec)

B) 80% of all Answered Calls be answered within 30 sec.(exclude abandoned calls)

If you do not exclude abounded calls and a client abandons the call after 30 sec you get “punished” twice, 1 for losing the call and 2 for not answering the call within the 30sec.


Perhaps a more management friendly view would be to subtract calls that abandoned within service level from the equation.

(calls answered within SLA) / (total calls offered - calls abandoned within SLA)

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