Backoffice FTE Calculation

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Can someone help me to calculate FTE for a Backoffice process which manages Service Requests for a telecom process.


Monthly Volume - 50000

TAT - 100% closure in 24 hours

AHT - 12-15 mins

Thanks in advance


Call Centre Helper

Statistically 100% is not a target that you can work to as there will always be an exception. I would say that 99% or 95% would be more accurate.

First you need to split the month down into individual days of a 24 hour period. You would also need to specify how long the working day of one person is (hours per day).

I presume that you are looking at target completion time rather than answer time and that an item of work could be interrupted over say a break period and come back to it later?

Let us know these details and someone could probably work out an answer.

Hello Jonty,

Thanks you for your response.

I am looking to meet SLA - which is defined as 100% of requests to be responded within 24 hours. I agree statistically we can target 99% in 24 hours too.

Working hours of FTE - 9 hours login with 1 hour break.

Since this is a backoffice process the activity can be interrupted or can be worked on later.


Call Centre Helper

Erlang calculations
Both of my calculations come out with the same figure - 122 agents
Method 1 - Simple division of the day (ignoring service level)
50000 emails per month

2500 emails per day (assumes 20 working days in month).
8 hours per day

480 minutes per day

28800 seconds per day
312.5 emails per hour
15 minutes per email

4 emails per person per hour
78.125 Agents needed
Add in shrinkage of 35% gives 122 agents
Method 2 (Using Erlang Calculation)

Incoming calls 313

in a period of 60 Minutes

AHT 900 Seconds

Required Service Level 99 Percent

Target Answer Time 28800 Seconds
77 Agents needed
Add in shrinkage of 35% gives 122 agents

Thanks Jonty for the response, appreciate it. :)

Workforce Planner

Just to understand this a bit better, although I agree with all calculations etc for both approaches, shouldn't occupancy be added into that as well ?

I do understand that the shrinkage depends on every company policies/breaks etc. However even in the case of e.g. an agent/employee being logged for 1 hour and not taking any break, we can not expect that those 60 minutes will be 100% productive , usually the occupancy would be somewhere around 73%. i.e. 43.8 minutes instead of 60.

Isn't that the way it should be calculated (or in general, a management decision on how much they are willing to push occupancy e.g. 80%-90%) ?

I got a different answer
I followed the calculation 78.125/(1-0.35) = 120, and 78.125/0.65 = 120. Where did I go wrong?


Call Centre Helper

Well spotted
Yes I agree that they both came out as 120. I think that I had punched 34% shrinkage into my calculator instead of 3%.

4 emails per person per hour

how did you get 4 emails per person per hour


Call Centre Helper

Divide and hour by 15
1 hour = 60 minutes
15 minutes per email
60/15 = 4 emails per person per hour

New Team Transition stage

On to the above FTE calculation for particular activity brings the required understanding. However would like to know how the FTE calculation is done for multiple activity which may be execute in different stage like Weekly Monthly Qtly Anually and also activity completion hours would be different.

Await for response



On 80% Occupancy
You require 97.65 on phone advisors and with 35% shrink you need 150 FTE. Moreover Just want once information from you whether its 24/7 process or its closed on weekend.

FTE requires for 48 hour TAT
The above scenario is true for a 24 hour TAT target. What would be the FTE required if the TAT target is increased to 48 hours? This is a very recurring question in most businesses but I never was able to find a good answer. Hoping someone can help. Thanks in advance.

How to calculate FTE to handle email with 4hr TaT
Hi ,
I am applying below formula to calculate FTE, but not sure how to add TAT factor
Daily Email 1342
Shift : 8 hrs
Occupancy : 85%
Shrinkage : 30%
AHT : 7 min

FTE : =(7*1342)/(8*60*85%*(1-30%))
FTE = 32.86

Any help on this really appreciate , Need to add TAT factor,


Call Centre Helper

TAT = Turnaround Time
TAT = Turnaround Time

It would be better if you used an Erlang Calculator

So instead of 80% of calls answered in 20 seconds you are looking for 80% of emails handled in 4 X 60 X 60 = 14400 seconds

How to apply Turn Around time in excel formula
Thank you for your reply
I have tried Erlang calculator , and change Target Answer time as 14400 or 21600 ie 4hr and 6hr , but there is no change is result,
How can I apply this factor while calculating in excel spreadsheet

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