FTE Calculation For Monthly Volume

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FTE Calculation At A Monthly

How can I use Erlang to find the right number of FTE for a monthly volume? How can consider the fact that the call center is open during 12 hours but the employees work 7 hours. Do I need to adjust the supply par 30 minutes in considering the fact that an employee work 7 hours instead of 12 hours? Does my question is clear? Sorry my first language is french, I do my best in English. Thank you so Munch. Here is the data: 27 355 calls per month, 21 workings days, service level 80, Target answer time 20, AHT 302.3. So to consider the situation, my supply by 30 minutes is:(27 355/21/6.5)*30/60 = 100 Am I right? The number of FTE according to Erlang C and this data is: 21

Question asked by Patrice

You Need to Create A Weekly Daily and Hourly Profile

There are approx 4.2 weeks in a month, so approx 6510 calls per week.

But across the week the calls are not distributed evenly. So a typical breakdown

Monday 23.8%

Tuesday 20.8%

Wednesday 19.8%

Thursday 18.8%

Friday 16.8%

So for a Monday you would have 23.8% x 6510 = 1549 calls

If you put this into the Erlang Calculator


1549 calls, 12 hours, 302.3 seconds 80/20 service level gives a peak of 31.5 Agents (21.5 Agents average across the 12 hours).

With thanks to Jonty


Thank you for your answer. However, I’m looking for the right number of employees to hire to meet that demand. My answer is 21 and 30 employees with a shrinkage factor of 30%. What do you think about that.

Thank you

With thanks to Patrice

To Get An Accurate Number You Would Have to Do Your Own Modelling of Demand

21 employees will leave you understaffed.

To get an accurate number you would have to do your own modelling of demand.

Try to find the call arrival patterns, which days, which hours etc and then you can get a more accurate figure.

With thanks to Jonty


I’M looking for the hiring plan. For the moment, the objective is not to break down a day by interval. I’m working on the long term plan. Considering 30 resources so 21 FTE, I will not be understaff. Il will not cover all interval but this is the right number that I need to meet the service level. I don not want to be overstaff. Here is the proof that the demand for the months will be cover with 21 FTE: 21 * 7 hours by day* 11,91 calls per hour(3600/302.3 AHT)*21 business day: 36 766 potential calls to be handling. This potential volume is higher than the demand of 27 355. What’s wrong? Thank you so munch

With thanks to Patrice

You Assume That All Calls Arrive Evenly Spaced Across the Day

Call volume varies across the day. You also need to take account of shrinkage.

Use this tool to help you


With thanks to Jonty

Is It Possible to Do…

Is it possible to download this tool? Thank you

With thanks to Patrice


My objective is to find the number of resources to hire at the beginning of the year. I Know that the call volume varied across the week and day. Once I have found the right resources to hire, I’ll Schedule the resources to minimize shortfalls. However, I do not want to cover the max interval or to be staff to cover all intervals of Monday because I’ll be overstaff for the rest of the week. I want the mean of resources needed. Do you understand my position? I think you can use Erlang C at high level (monthly) to find the right number of resources without to check by interval. Scheduling by interval will be the next step. What do you think about that?

With thanks to Patrice

Scheduling By Interval is Good

There is an excel version of the Erlang calculator but it is not as functional as the online version: New Excel Based Erlang Calculator – with Maximum Occupancy

With thanks to Jonty

FTE Calculation

I want to calculate the FTE head counts for a months. The vendor is required to give 8*6 60 staffs and 60 staffs in 8*7

With thanks to selwyn

Read This Article

Follow the instructions in this article How to Work Out How Many Staff You Need in a Contact Centre

With thanks to Jonty

Author: Jonty Pearce

Published On: 12th Apr 2022 - Last modified: 21st Apr 2022
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