Empowering contact center excellence for 30 years!

Service Level Calculations

Service Level

Jul 01, 2002

I need your assistance in a benchmarking survey I am currently conducting for the service level formula of our inbound queues which is currently as follows:

Service level = {[(AN + AB) - (An + Ab)] / (AN + AB)}* 100 %

AN is total answered calls
AB is total abandoned calls
An is answered calls after threshold
Ab is abandoned calls after threshold.

In our formula, calls abandoned before thresholds will increase the service level. Would you please provide me with the most popular service level formulas used in call centers? -- Ahmed Gamal


  • Posted at 12:00AM on Aug 1, 2002

    There are a number of different ways to calculate service level. In general, based on my own experience as a call center director and from clients I have worked with in my consulting practice, I have seen five different ones used. They are shown below, along with an example for each so you can see the different outcomes.

    I will also add that the key is to know and understand what you are truly measuring. It is also very important to track and trend the measurement on a half-hourly basis because it is at this level where you can truly begin to troubleshoot, make improvements and keep the positive actions going.

    Example data: Your service level target is to answer 85% of the calls in 30 seconds (I chose these numbers randomly):

    Total calls answered = 1000

    Total calls abandoned = 60

    Total call answered within 20 seconds = 860

    Total calls abandoned within 20 seconds = 20

    Total calls abandoned after 20 seconds = 40

    Total calls abandoned within 5 seconds = 10

    Formula #1:

    Service Level = {(Total calls answered within threshold +calls abandoned within threshold)/(total calls answered + total calls abandoned)} * 100%

    This calculation takes all calls into consideration; however, calls that abandoned within your service level threshold count positively, meaning they help increase your service level percentage.

    Example: (860+20)/(1000+60)*100% = 83%

    Formula #2

    Service level = (Total calls answered within threshold) / (Total calls answered)*100%

    This formula ignores calls that abandon. Clearly this is NOT an accurate reflection of what is going on in the center and is not one I would recommend, nor would any other people I work with.

    Example: ((860)/1000))*100% = 86%

    Formula #3

    Service Level = (Total calls answered within threshold) / (Total calls answered + Total calls abandoned)*100%

    Here you are given “credit” for all the calls you answered within your service level threshold and all calls that abandon will affect service level negatively, regardless of when they abandon.

    Example: ((860)/(1000+60)) *100%= 81%

    Formula #4

    Service Level = (Total calls answered within threshold) / (Total calls answered + Total calls abandoned after threshold)*100%

    Here calls that abandon after the threshold affect service level negatively. Call that abandon before the threshold do not affect service level.

    Example: ((860)/(1000+40))*100% = 83%

    Formula #5

    Service Level = {(Total calls answered within threshold +calls abandoned within a shorter amount of time than the threshold)/(total calls answered + total calls abandoned)} * 100%

    This formula uses a threshold to account for "short calls." For example, if your threshold is 20 seconds, here you would say that calls that abandon before that time will count positively towards service level.

    Example: ((860+10)/(1000+60))*100%= 82%

    I hope this helps.

    -- Rose Polchin, President, RPolchin Consulting and Training, Certified Associate, Incoming Calls Management Institute, Tel. 201-652-0443, Fax 603-806-8162, rpolchin@att.net

  • Posted at 12:00AM on Sep 1, 2002

    I have a question about the calculation of service levels. In the company I work for, we calculate two kinds of service levels:

    "Service Level 1" which is calculated daily
    "Service Level 2" which is calculated monthly

    These are the formulas for each one:

    SL1 = Total calls answered/(total calls offered - calls abandoned within 6 seconds)

    SL2 = Calls answered within 20 seconds/(total calls answered + calls abandoned after 20")

    Are these formulas used by other call centers? Do you suggest other, more effective formulas, maybe?

    Thank you. -- Cecília Martins

  • Posted at 12:00AM on Nov 1, 2002

    I have questions and comments about the service level formula and comments in Rose Polchin's response below:

    "Formula #2

    Service level = (Total calls answered within threshold) / (Total calls answered)*100%

    This formula ignores calls that abandon. Clearly this is NOT an accurate reflection of what is going on in the center and is not one I would recommend, nor would any other people I work with.

    Example: ((860)/1000))*100% = 86%"

    Why is this NOT an accurate or popular formula in your mind? Other formulas take into account calls that abandoned before the threshold and have them reflect positively on service level. My opinion is that the latter is not a fair depiction of service level. If calls abandoned, why should you get credit for them on your service level? If anything, they should not be included as in the above Formula #2, because you cannot "guess" what would have happened with the call.

    Thanks for your help. -- Aaron McLean

  • Posted at 12:00AM on Dec 1, 2002

    The second formula listed by Rose Polchin, below, only accounts for calls answered. I just don't like this one as much, since you are only measuring the ones that you answer. What about those that waited for 15 minutes and gave up? That is a customer that didn't get answered within your service level objective. Therefore, I would use the calls offered in place of calls answered, or the formula in the original question, above.

    I typically use a very similar formula: (Calls Offered - Calls Delayed) / Calls Offered. Calls offered includes both answered and abandoned, with calls delayed being those delayed after your delay threshold in the ACD. Hold this helps. It should produce the same result as you have, but I think it is easier to use, since I like the simple approach. -- Doug Charles, Access Integrated Networks

  • Posted at 12:00AM on Jan 1, 2003

    Service level equations have been bantered around for years with each vendor calculating it differently and most of them allowing you to create your own calculations. I have been teaching ACD report statistics for over 12 years now and it is amazing how often people do not understand the metrics they are looking at or even how they are calculated. The four standard service level equations have been used by many call centres - yes, even the one that only counts answered calls! Though I do not recommend this calculation to my clients, it is still valid - as long as other factors are considered, such as the call abandoning breakdown, busy out breakdown and so forth.

    In answering Cecilia Martins' question, about which equation to use, my comments are I would use the same equation for the interval, daily, weekly and monthly calculation, i.e. SL2.

    SL1 = Total calls answered/(total calls offered - calls abandoned within 6 seconds)

    In this equation my question is, what constitutes calls offered? Is it answered, abandoned, busied out, etc.? It also looks like all calls answered are positive, so even if the caller waits 120 seconds or more it affects this equation positively. There is no threshold setting. It looks like you are also subtracting the "fast clear downs" or those callers who waited only 1 ring (approximately 6 seconds in the North American ring cycle) and hung up. Another term that has been used is quick abandons. (Note that Rose refers to this type of call as a short call; be careful if you use Nortel Call Centre products, because a short call in their vendor definition is a call that has been answered by an agent and then disconnected by the agent or the customer within a system defined threshold.) As with any vendor, get what is usually called their Data Dictionary that lists all the data fields, calculations and statistics groups or data views available within your system. It may be better to call SL1 Calls Handled %, instead of Service Level, because you have no threshold to meet and you seem to be attempting to just measure customers you answered, no matter how long they waited, divided by the number of calls 'offered' less the 'fast clear downs' or quick abandons.

    SL2 = Calls answered within 20 seconds/(total calls answered + calls abandoned after 20")

    In this equation, you are calculating what Rose refers to as Equation # 4 - your threshold is set to 20 seconds.

    Service Level Equation 4 = (Total calls answered within threshold) / (Total calls answered + Total calls abandoned after threshold)*100%

    This equation is quite common among the call centres I have worked with, when their threshold is set at around 20 seconds - or 3 rings in the North American ring cycle. (Note: If your threshold gets greater than 40 seconds this MAY not be a valid equation to use.) Again, if the customer chooses to hang up after waiting less than 20 seconds, the companies decided NOT to count them in their service level; however, they still calculate the % of all callers that did abandon less than the 20 seconds. This is included in their reports. They don't ignore data.

    I will be giving an ICMI web seminar on this topic - which will discuss service level equations and how they are used - and I suggest you join in. We tend to offer this seminar twice per year since there are always new people coming into the centre and they need to understand the ACD data they are getting.

    -- Cheryl Odee Helm, Call Centre Consultant, Certified Associate, Incoming Calls Management Institute, Tel. 905-985-4555, Fax: 905-985-4391, cphelm@sympatico.ca

  • Posted at 12:00AM on Sep 1, 2004

    I'm surprised by the amount of debate on this forum on how to calculate the service level. After reviewing, I can see why people may have a difference of opinion. While there is universal agreement that you take the number of calls answered within a set goal as the numerator, it is unclear what you are measuring it against, the denominator. Do you divide by the number of answered calls, the number of calls offered (Answered plus Abandoned), or those that are answered and those that abandon after some set threshold? Options, options, options.

    Before I state my opinion -- I'm sure you're all sitting at the edge of your seat --first an analogy: The Swiss Army Knife. Sure, it can do many many things, but in order to have so many options, it doesn't do anything extremely well. The can opener can do the job, but I still find it useful to have a tool that is uniquely a can opener at home. Specialization in tools helps isolate and resolve specific issues. The same is true for metrics.

    Each metric should primarily focus on one key idea, if it has secondary implications, great. Abandon Rate tells you how many customers are not getting service. Average Abandon Time can measures the sensitivity of your callers. Max Delay highlights your worst case scenario (or baseball fans may call it Uecker Service).

    In my opinion, service level is really telling the percentage of those who were "serviced" within a certain time goal. Those who abandon - after any amount of time - were not serviced. Since you already have a primary measurement for Abandon Rate (or if you don't have it, you may want to look into it), I would exclude all the abandoned calls within this measure. One measure, one primary focus.

    But then again, I don't let my foods touch either. -- Scott Sandok

  • Elena Garay Posted at 12:00AM on Jul 11, 2005

    I have a related question. We're doing email support with different thresholds per ticket depending on the customer's subscription plan. How do you compute for a weighted Service Level or Response Time? Doing an overall Service Level or Response Time doesn't seem to give us an accurate picture of what's happening. -- Elena Garay

  • Monis Posted at 12:00AM on Feb 10, 2006

    I am supervising the call centre here and all what I want is the exact equation applied to find the service level. I have tried the above solution and the outcomes did not match. Please see the figures here: Calls presented to queue 13,383 Calls Handled 11,618 Agents seated 42 Average handle time in seconds 55 Average wait to answer 27 seconds Time to abandon 30 seconds Now, in my system it shows that my service level for that day is 53%. Is there any chance that you would guide me to get the equation adopted? Regards -- Monis, Asia

  • Jasmin Wilkins Posted at 12:00AM on Sep 8, 2006

    Regarding Service Levels - if the goal of this metric is to convey a measure of the level of service from a customer perspective (usually targets are aimed at ensuring customer experience is of an acceptable standard) then in my experience, abandonment should be reflected. For a customer, abandonment is usually due to unwillingness to tolerate delay. If this experience is excluded, Service Level does not truly reflect customer perception. If only answered calls are being used, then the metric name should reflect this (perhaps Answered Grade of Service) to ensure it is not interpreted incorrectly. Senior Management often only get a couple of metrics, and tend to take them at face value. Further, not including any abandonment inflates the value somewhat as well - and can make it difficult to ask for the extra staff you need if you have service difficulties! Historically, the reasoning for the calculation I normally use is as follows: Calls Ans or Abandoned after the threshold did not meet the target, regardless of the end condition. Calls Answered prior to target meet the target. Calls Abandoned prior to the target are excluded, as had they continued, they may or may not have been answered. Hence, I prefer (Ans < t)/(Offered - Aban < t). This results in a metric that reflects both delay to answer, and abandonment, and their impact on customer experience. -- Jasmin Wilkins, MSD New Zealand

  • Martin Shirlaw Posted at 12:00AM on Mar 9, 2007

    Although all these are valid service level calculations some look to be flawed to me. I do agree with comments indicating that different metrics are required for various aspects of call centre reporting. A very basic service level calculation I would lean towards would be: Calls Answered within service level/(Calls offered - Calls abandoned < 5-6 secs) The 5-6 secs threshold is simply to catch wrong number calls, etc. Other abandoned calls should not be built in to this calculation; rather there should be another metric for this as mentioned above. The abandoned rate metric would be calculated like this: (calls abandoned - calls abandoned < 5-6secs)/(Calls offered - Calls abandoned < 5-6 secs). In regards to the poster with the 53% Service level, can't really help unless you give your calls answered in service level. Thanks -- Martin Shirlaw, Scotland

  • Stats guy Posted at 12:00AM on Nov 30, 2007

    Interesting discussion on service levels. Calls abandoned within threshold can be considered successfully "serviced", because the caller thought they no longer need to stay on line. For example, they may have heard an announcement that clarified something simple, like opening hours. That information served their call, so they hung up. Another example would be that the caller heard an expected waiting time prompt, and decided their call was not worth waiting for. In other words, they decided they no longer needed the service of the call center. As a follow up question to the group, does anyone know a good service level formula for an E911 call center ? In these call centers, a call can be both abandoned AND answered. This is to handle the case where the caller's phone burned down (as an example). The half-call is still routed to an agent so that ANI can be obtained, and the emergency response can be dispatched. In this case, how should abandons affect service level, if at all?

  • blujays Posted at 12:00AM on May 19, 2008

    Abandonment rate would be reflected in the Accessibility calculation and Average Speed of Answer. Service Level in my opinion should be on calls answered/handled only. Without looking at all calculations it would be hard to get a true picture.

  • Mahesh Punia Posted at 12:00AM on Jun 2, 2008

    There are 3-4 alternative formulae being used for calculating and reporting service level performance in a contact center. Before we consider the right / most preferred formula to use, it is important to make note of a few points: 1. Make sure that the formula programmed in your ACD is the same as the one that you are using. 2. Make sure to use the same formula consistently throughout all your planning and calculations. In case you are subtracting your abandons while reporting your performance, make sure that you are not including these in your forecasted calls (usually most forecasting teams make this mistake), else you are actually budgeting staff for a higher call load (answered + abandons) whereas reporting performance against different count -- not a fair practice. 3. While reporting service level performance, using end of day simple average or weighted average is not the best indicator of your performance from a customer’s perspective. It is best to report consistency of service level performance, which is the percentage of intervals in which the per interval service level was met. The preferred formula for service level is the basic one – (Total calls answered in Y seconds) divided by (total calls offered). -- Mahesh Punia, LiveBean Consulting & Training

Please sign in to contribute an answer. If you don't have an account you can register for free here.

Question Search

Need help with something specific? Search our entire QueueTips section to find it.

Can't find what you're looking for in a current QueueTips post? Submit a new post to us!