# Service Level Calculation in Erlang C Excel Calculator

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When using the Erlang C - Service Level Calculation in Excel the result does not appear as per the service level target of 80%? Can you Help?
Looking to calculate the service level per interval. I expect to see 80% as my result.

I have
50 calls in a 15 minute interval
80% service level
20 sec ASA
1000 secs AHT
27.5% Shrinkage
= 88 FTE

When i use 88 FTE for my planned FTE for the that 15 minute interval i get 100% service level using the erlang Service Level calculation. --example =ServiceLevel(1,2,3,4,5)--

Why does it not display the 80% I wanted based on my FTE forecast. I know it does not include shrinkage in the service level calculation so if reduce my planned FTE by 27.5% i get circa 84% Service level forecast.

So do i need 88 FTE or do i need 63.8 FTE, i believe its got to be the 88 FTE however do i calculate the service level off the 88 which gives me 100% SL or do i calculate it off the 63.8 FTE which gives me 84% SL as i only want to achieve 80% SL.

Many Thanks

Neil

Helper

Call Centre Helper

The difference is shrinkage
The AgentsFTE function includes shrinkage, but the ServiceLevel function doesn't.

So if you set shrinkage to zero, then they will both produce the same answers.

So the answer is 64 agents before shrinkage and 88 agents after shrinkage.

So the correct answer is 88 FTE. You can see the results more clearly in the online version.

The 80% SL target vs the 100% SL prediction
Hi Jonty,

Thanks for the quick response. I believe we are in alignment on all the points above which is great.

What service level target would you publish to your stake holders, the 100% based on the FTE inc shrinkage or the 80% based on the FTE excluding shrinkage? or both FTE?

Many Thanks

Neil

Helper

Call Centre Helper

You should publish the 80% service level
The 64 agents before shrinkage is the same as 88 FTE including shrinkage.

In essence what you are saying is that you need 64 people on the phones, but because at any given moment some will be away on holiday, some will be having training, in a meeting etc you need 88 heads in the business.

If for some reason 88 people were at work at that moment (e.g. nobody was on holiday, nobody was in the loo or getting a coffee, nobody was in training, meetings or coaching - then your service level would be 100%).

But shrinkage can vary by time of day and day of week (more people take holiday on a Friday afternoon than a Tuesday morning) and also by month - more people get sick in winter and more people take holiday in August and December. So you could vary your shrinkage figures based on those factors.