FTE Calculations

Calculating the number of Full-Time Equivalents (FTEs) in a call centre can be complex, especially when factoring in call volume, service levels, and working hours.

Stells reached out to our community of industry professionals for help to calculate FTEs in a call centre:

I need to calculate the number of FTEs in a Call Centre.

What I have is:

• Number of Inbound Calls per Month is 1,320,000
• AHT is 120 Seconds
• Service Level 85% in 20 Seconds
• 1 FTE is 172 Hours per month.

How many FTE do I need?

Question asked by stells

You Need the Erlang Calculator

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).

Here is a link to an Online Erlang Calculator

Also here is an Excel based one – I’ve entered in the figures you provided and for these requirements, you would need an FTE of 474.3.

Here is an example of how you would work out the required FTE using an Erlang Calculator.

With thanks to Jonty

How Can I Work Out My FTE Requirements?

I need assistance regarding working out my FTE requirements:

• Expected call volumes: average volume of 74,000 per month
• Service Level : 75% within 60 seconds
• AHT: 180 seconds
• Support hours: 9 AM to 2 AM = 17 Hours

How many FTEs do I require for this?

7 Day Operation With 5 Day Working Weeks

Similarly if its a 7 day operation, how many FTE do we require if all agents will be working 5 days per week?

With thanks to rabby

The Best Way to Do This is Through Erlang Calculator

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 Erlang Calculator – I’ve entered in the figures you provided and for these requirements you would need an FTE of 40.3.  You can also improve the accuracy of the Erlang Calculator by adding in specific details under advanced options to take into account occupancy, shrinkage, etc.

Look At Your Traffic Profile for 7 Days a Week

It tends to depend upon your 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.

With thanks to Jonty

Is This FTE Calculation Correct?

• 17000 Calls
• 120 Seconds handling time 
• 8 login hours in a day

Is this FTE calculation correct?

• 17000 * 120 = 2,040,000
• 60 Minutes * 60 seconds = 3,600
• 8 * 3,600 = 28,800
• 2,040,000 / 28,800 = 70.8333

With thanks to RAHUL

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

• 17,000 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 1,312 calls per half hour.

• Maximum Calls per Period: 1,316
• 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 using this Free Erlang Calculator

With thanks to Jonty

How Do You Calculate Number of Agents Required for Emails?

Can I apply the Erlang Calculator to calculate how many agents I need to complete incoming emails in a contact centre?

For example, we are to receive 1200 emails in a period of 24 hours, we work a clean 8 hours in a day and our average responses per hour targeted is about 6.3 emails.

We are targeting a SL of a minimum 85%. If the Erlang Calculator is not suitable, is there any other recommended tool? Thank you very much in advance!

With thanks to Teena

Erlang Calculator Can Also Do Emails

Yes you can also use the Erlang Calculator to work out emails as well, or you can add it into the Multi Channel Simulator

With thanks to Jonty

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You might also find these articles helpful to read next:

• How to Calculate FTE Requirements Based on Volume
• How to Calculate Required FTE for Inbound Call Volumes
• FTE Calculation for Chat

Author: Jonty Pearce
Reviewed by: Hannah Swankie