FTE Calculation Question

FTE Calculation
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FTE hours requirements

I have seen FTE hours requirements calculated two different ways when factoring in an 80% occupancy.

Grossing up by 20%

1)((NCO x AHT)/3600) x (1+(1-OCC))

Dividing by 80%

2)(NCO x AHT)/OCC/3600

Using 1000 calls, 600 AHT and 80% OCC, the first equation equals 199.99 hrs.

The second equation equals 208.33 hrs.

Which should I be using?

Question asked by shmeek07

Adding and subtracting 20%

It looks like you have the classic problem of adding and subtracting 20%.

If you add 20% to 80 you don’t get 100% – you get 96%.

But if you take 20% of 100 away you get to 80%.

Occupancy is always worked out as a percentage of total time.

So Total time * Occupancy (as percentage) = (NCO * AHT)

Where NCO = Number of calls offered

and AHT = Average Handling Time. You then just need to make sure that they are both in the same unit of time.

Number 2 is the correct answer.

With thanks to Jonty

Off Phone Shrinkage

Thanks for getting back to me;

So taking this one step further, because off phone shrinkage like break/lunch/coaching/training is not part of the call handling time, am I ok to use the gross up method, and just multiply by 1.15 if i want to increase my required hours by 15%?

Same question for grossing up for planned absence/vacancy?

So basically,

1000 calls * 600 aht / 80% / 3600

= 208.33 hours

w/shrinkage of 15% (x 1.15)

= 239.58 hours

w/absents of 10% (x 1.10)

= 263.54 hours

Or should I be dividing by 85% for shrinkage and 90% for absence?

Thanks for the clarification.

With thanks to shmeek07

Work Down from the Total Amount of Time

You always work down from the total amount of time. i.e. 3600 seconds in the hour. 15% shrinkage is 540 seconds. 10% absence is 360 seconds.


100% of available time

– 15% Shrinkage

– 10% Absenteeism

– 20% Idle time

– 10% Wrap Time

– 45% Talk time

= 0

It’s much easier to visualise it if you plot it on a pie chart. This way it always adds up to 100%.

Please note that absence is normally included in shrinkage. The formula for shrinkage is (planned leave + unplanned leave + away from post)/roster for the day

With thanks to Jonty

How many FTE would you need to do the above job and what would be the proper calculation?

I have two questions about FTE calculations and call capacity

1. If your data is as such

FTE 740

FTE hours/month 168

Load factor: 25%

Expected occupancy 70%

expected AHT 350

How many calls can the above call centre take with those metrics?

what would be the proper calculations because i see more then one somtimes

second question

Call Volume/Month: 345,000

Abandon Rate: 5%

AHT: 348

Expected Occupancy: 55%

Load Factor: 30%

FTE Hours/Month: 170

How many FTE would you need to do the above job and what would be the proper calculation?

With thanks to noah

Use an Erlang Calculator

The easiest way to do all of these calculations is to use and Erlang Calculator.


Thanks to Jonty


740*168 = 124320

After Occ = 124320*70% = 87024

Less Shrinkage = 87024*(1-25%) = 65268

One Call Time = 350/60 = 5.83 Minutes

Probable # in one Hour = 10.29

# of calls answerable = 65268*10.29 = 671328

By the way, your shrinkage and Occ are both raising enormous cost to you though it entirely depends on your project’s operational requirement. If you can manage, keep them Occupancy = 80%, Shrinkage = 20%

Leaving your second question because turning around this answer delivers your second objective.

With thanks to sushil10s

A Weighted Average of Those SVLs?

thank you very much,

another question if you have SVL of 93% , 66% and 72% and you wanted to get the weighted average how do you do this if you have no information of calls offered or answered, all you have is SVL. Can you still get a weighted average of those SVLs?

With thanks to noah

Weighted Avg

Weighted Avg % is actually the sumproduct of those numbers and percentage which is the case here. So you will have to know the numericals of offered/answered calls as far I know.

With thanks to sushil10s

Calls Offered Divided by Sum Calls Offered

thats right because SVL=calls offered divided by sum calls offered.

Also another question with respect to the third post up. If i wanted to find cost per call and the cost that the company was paying was 25 dollars per productive hour, i would just take the Probable # in one Hour = 10.29 and then take the 10.29 and multiply it by 25 dollars is that correct?

With thanks to noah



With thanks to noah

Find Workload Hours

I have a Question why do some use this equation(NCO x AHT)/OCC/3600 to find workload hours? when at times i see it being used to find how many calls the agents can take iam a little confused, for example some say if call centre takes 100 calls in 30 minutes and each call takes 3 min or 180 seconds how many calls would these reps take, i would say 10. May you please clarify this for me?

With thanks to noah

Include Wrap Time

Is wrap time and absence both a part of shrinkage?

also idle time 20% i am guessing this is occupancy which usually may be 80% so that leaves 20% idle time correct?

With thanks to noah

Handled Calls By Each Rep

if you have 100 calls in 30 min then 1800 sec so agents required will be 10 reps handling 10 calls each

100*180=TT 18000/1800=10 resp and 100/10 = 10 calls each

With thanks to Khem

FTE Required

Annual BAU Attrition 65%

FTE Hours per Week: 40

Shrinkage: 25%

Occupancy: 90%

Headcount Campaign 1 76

% Competent 65%

On what basis do you want to calculate the FTE ? It should be on basis of contacts received in Week or month

With thanks to Khem

How to Do a Calculation to Find Out the Headcount Required

Hi, Below are figures and I am unable to find how many HC require to answer 10000 calls at the AHT of 150 seconds with occupancy of 85%. Also please add Shrinkage on the same as 15%

With thanks to Milind

Use an Erlang Calculator

The easiest way to do all of these calculations is to use and Erlang Calculator.


Thanks to Jonty

Author: Jonty Pearce

Published On: 12th Apr 2022 - Last modified: 14th Apr 2022
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