FTE Calculations

Topic Views - 24982


Infinity Communications

I'm required to calculate the number of FTEs in a Call Center.

What i have is :-

Number of Inbound Calls per Month is 1,320,000.

AHT is 120 Seconds

Service Level 85%

1 FTE is 172 Hours per month.

Please help


Call Centre Helper

You need to break down the calls by half hour and then you need to use a call centre calculator. (This is often known as an Erlang calculator).


WFM Analyst

Hi Stells,

I'm new to workforce, this will be what i will do according to the available information. Will be more accurate if plan shrinkages and occupancy can be provided as well.

Volume 1320000

AHT 120

Total 158400000

Total Hours 44000

FTE hours / Month 172

Total FTE Needed 256

WFM Analyst

Hi Jonty,

I notice you had give alot of valueable advise in different posting.

Would like to seek your advise for this.

I had make some calculation for Manual VS ErLang C ( which consider SLA & Waiting time ) but manual calculation didnt.

Below are my finding. Above 256 FTE was manual and without consider SLA & waiting time.

i make by default 20 sec waiting time allow. and below will be the SLA target and how much of additional FTE needed compare with manual. 85/20 SLA will need additional 58% FTE.


100 481%

90% 67%

80% 51%

70% 41%

60% 33%

50% 27%

Please share your thought.


Call Centre Helper

Hi Ivan

The manual calculations are usually wrong as they do not factor in the call arrival patterns and assume that the call volume is even across the day and that there is no service level calculation.

I would always take the Erlang output over a manual calculation.

WFM Analyst

Hi Jonty,

Yes, agree with you advise. But i do have another concern that in the situation if the business unable to provide the half hourly volume, i can only use the manual calculation method that include shrinkages and OCC.

And if i juz average the volume to 48 interval since 24 hours, the FTE require will not be accurate due to call arrival pattern as you advise.

Threfore, i would like to find out how to make the manual formula calculation result get closer with Erlang C ( with SLA consideration ). Thus, i had make some research and trial which giving me if i want 90/20 will need to add in additional 67% FTE in the manual calculation or 80/20 will be addition 51%. This result are finding using Erlang C calculation with weekly volume by interval volume and AHT compare with manual calculation juz use above method.

Hi Ivan,

Please help me out as I need your assistance regarding FTE requirements:

Expected call volumes: average volume of 74,000 per month

Service Level : 75% within 60secs

AHT: 180secs

Support hours: 9am to 2am = 17 Hours

How Many FTEs do I require ? Please help. Thanks in advance


Call Centre Helper


The best way to do this is using an Erlang Calculations.

You first need to split your calls across a week and then by hour to match your profile. You then use the Erlang spreadsheet to calculate the raw number of people you need every hour.

There is a spreadsheet here


There is also an online version here


Thank you so much Jonty.That was really helpful.

If its a 7 day operation, how many FTE do we require ?

All agents will be working 5 days per week. Thank you so much for your help.


Call Centre Helper

It tends to depend upon you traffic profile.

I tend to find that on average 22% of the volume comes in on a Monday and that tails down to 17% by Friday. You will also need to work out your daily call arrival profile. You can probably get this off your current phone system.

You will also need to build in a "shrinkage factor" typically around 50-70% to allow for time off phones such as meetings, holiday, sickness etc.

FTE Calculation Help

-New Business begins Oct 1st
-530,000 Members
-Hours of Operation = M-F 8a-5p CST
-Monthly Utilization = 10.5%
-Avg handle Time = 645 seconds
-SLA = 80/30
-Shrinkage = 27%

Solve for the following:
1. What is your expected volume for month 1?
2. What is your average daily volume (will take volume or adjusted volume) for month 1?
3. What is your base FTE need?
4. What is your Adjusted Schedule FTE (hint, hours of operation; use 30 minute lunches for your schedules)?
5. What is your Staffed FTE Requirement AFTER shrinkage?
6. Using your average daily volume, build out how you expect your day to look (by 30 minute interval) for the entire day; include your FTE needs by interval as well (use a straight 645 second handle time).

Required FTE
CALLS*AHT = 1320000*120 = 158400000 = WORKLOAD
CONVERT WORKLOAD INTO HOUR = 158400000/3600 = 44000
FTE = 44000/172 = 255.814 = 256(APPX.)


Call Centre Helper

Your required FTE is wrong - use Erlang, shrinkage and max Occupancy to get the right figures

You have just put in the traffic intensity to get your answer of 256 FTE

You have not included these three factors
- Service Level
- Shrinkage
- Maximum Occupancy

You need to use an Erlang Calculator to work this out


1,320,000 calls per month = 303,448 calls per week.

You normally get around 23% of call volume on a Monday so this works out as 63724 calls per day.

Putting this into the Erlang Calculator shows that you would need a peak of 441 agents, which is significantly higher than the 256 agents you have suggested.

Required FTE
17000 Calls 120 Seconds handling time with 8 login hours in a day


60 Minutes*60 seconds= 3600



Hope this would help to answer easily.

Best Of Luck


Call Centre Helper

You have to break it down by interval

What you have worked out is the average traffic intensity. Unfortunately the average is not of much help.

You need to put this into an Erlang calculator

So Assuming 17000 calls per 8 hours - AHT Time 120 seconds - 80 % Answered in 20 seconds - Shrinkage 30 % - Max Occupancy 85 %.

This with a typical traffic profile gives as peak of 1312 calls per half hour.

Maximum Calls per Period 1316
Maximum Number of Agents 148.5
Average Number of Agents 127.8
Average Occupancy 79.2%
Service Level for Day 99%
Answered in 20 Seconds
Average Speed of Answer (ASA) 1 Seconds
Answered Immediately 91.4%

This is much higher than the 70.8 advisors that you suggest.

You must factor in
- Traffic broken down by interval (typically per half hour)
- Shrinkage
- Maximum occupancy

Try for yourself on this link

Want to add a comment?

Not found what you were looking for?

1. Try searching through our site.
2. Still not got an answer?

Why not ask the Call Centre Helper Community? Click here to ask your question