How to Calculate the Number of Agents Required in a Contact Centre

One of our readers recently asked “What is a good method of calculating the number of agents required to handle calls in a given time period?”

Here’s what our Community of industry professionals had to say:

There are Two Methods on How to Calculate the Number of Agents Required

There are two ways to calculate the number of agents you need.

1. The Easy Way – An Online Erlang Calculator

*The Method recommended by Call Centre Helper*

You can use an online calculator, such as our free Erlang Calculator for Contact Centre Staffing

2. The Hard Way – Doing it Manually – Without an Erlang Calculator

We have now written a comprehensive guide to calculating Staffing numbers – It covers all aspects of how to calculate headcount required, to find out more read this article: How to Calculate Staffing in a Contact Centre

We do recommend that you use a tool though

Contributed by: Jonty

Use An Erlang Calculator

Here is a really basic calculation:

(Handle Time x Calls) = Basic Seconds required

Seconds required ÷ shrinkage % = Total Seconds actually required

Total required ÷ Working seconds in day = Base FTE

BUT Remember this takes NO account of queuing or contact arrival distribution.

If you want to do manpower calculation in BPO the best option is to use an Erlang Calculator. This is a tried and tested formula to calculate the number of agents needed.

Here is a link to the Erlang C Calculator

If you need to use a spreadsheet, look at this one: Excel Based Erlang Calculator for Contact Centres – with Maximum Occupancy

You can just plug your numbers in there.

Contributed by: Dave Appleby

Guidance for Using Erlang

There are a couple of free excel based Erlang calculators that could do the job for as mentioned earlier.

If you still want to use Erlang, but not a calculator, we have written some useful guides explaining Erlang.

If you want to find out more about what is the Erlang C formula, this article walks you through the Erlang C formula: Erlang C Formula – Made Simple With an Easy Worked Example

This is a beginners guide to the Erlang A formula, and explains what it is, and provides more information on how to use it: A Beginner’s Guide to the Erlang A Formula

Contributed by: Jonty

Use A Headcount Model First and Then Erlang

I’ve always regarded this as two separate calculations.

If Erlang says you need 20 agents in a given half hour, then you put 20 on, obviously a bit of smoothing is required through some intervals as the volumes will vary.

Erlang is really for scheduling. I think what you are describing is a headcount model.

How to Calculate Your Overall Headcount Requirement

One simple way is just to add up the total calls each month, multiply by your AHT which then gives you the actual staff hours required.

Then add in an efficiency figure (basically this would be the inverse of your availability).

To that add on a percentage for sickness (use your own actuals), holidays (depends on entitlement, but you would expect 10-15%, then other shrinkage.

I allow 12% for breaks, etc and then a further 8% for Admin (1-2-1’s, meetings, etc) These were all cumulative figures – meaning you add on hols, then add on sickness and so on.

Take that result and divide by 147 (assuming your agents work 7 hours, 21 days a month).

What you will have is your overall headcount requirement (albeit just based on 1 month – but repeat to build up a pattern)

With your overall headcount done, then use Erlang to decide on how best to allocate those staff by way of shift patterns, etc.

The SLA is Built Into Your Scheduling

The SLA is built into your scheduling. One of the Erlang calculators would take care of that, you can access it free here.

The efficiency part is based on the fact that agents have available time waiting on calls. So if your available time is 10% then add in a 90% efficiency.

Your actual shift patterns shouldn’t affect your headcount requirement too much. It’s the same amount of work, but just spread over a different period (which comes back to your scheduling).

The 147 figure is just the number of hours that a full time agent would work in a month.

It will vary slightly depending on the actual working days, but given that you would never change your headcount month by month, then the figure is accurate enough.

Contributed by: Scott

Shrinkage is Cumulative

Some areas of shrinkage are cumulative whilst others aren’t. It also may vary from one company to another.

For example (and I’m going to use 10% just to keep this simpler) if an agent is paid for 260 days a year, you would factor in Holiday, taking them down to 234 working days, and then factor Sickness as 10% meaning 23.4 days, ending with 210.6 days.

This would actually translate as a practice where you are allowing agents to be logged as both sick and on holiday simultaneously, as the sickness calculation is reducing the total amount of resource you are loosing for other areas of shrinkage.

This would be correct depending on company practice, but some businesses say that is an agent is sick during scheduled holiday then the holiday would be given back to the agent to take at another point, in which case the sickness shrinkage should not impact on the total resource lost due to holiday.

It really varies from one category to the other. Obviously if an agent is on holiday then you wouldn’t count breaks for this time, so it would be cumulative, but a day of sickness or holiday typically wont result in their 1-2-1 being cancelled, so this would be a larger % of their remaining working time, or else done non cumulatively.

It can take a lot of thinking as to the order it should all be figured out in, to get the actual end result. It might only be a couple of % different, but for large centres this could be hundreds of pounds difference.

Contributed by: KevinP

Shrinkage After Holiday and Sick Absences

My calculations are based on assuming that (just using fictional figs) 10% of staff are on holiday and on top of that a further 5% are off sick. Then of those remaining available in the workforce, there is an additional shrinkage to be added.

You raise a fair point in that the actual calculations would differ from centre to centre, but this can at best only be an estimate.

I’ve never seen any headcount model that is more than that due to the variables involved.

Contributed by: Scott

Calculating Shrinkage

What Call Centre Shrinkage Is

According to Call Centre Helper Shrinkage is a measurement of anything that takes an agent away from their ability to take customer contacts.

For a more in depth look at the definition, read this article:

How to Calculate Call Centre Shrinkage

This article should help you with How to calculate contact centre shrinkage: What is Call Centre Shrinkage and How to Calculate It?

Contributed by: drogo8

Calculating the Staff Needed for More Than 1 Channel

It can be a bit tricky to calculate staffing for a combination of both Calls and Emails.

We have developed a multi-channel staffing calculator that will help you to develop staffing levels.

Click here to view the multi-channel calculator

You could also produce a weighted average handling time for both your call and staffing levels and then plug them into our Online Erlang Calculator or into the Excel Based Erlang Calculator

Contributed by: Jonty

Work Days and Time Off

What is the actual head do I need to hire if let’s say I need 50 agents per day and each of one of them has a 2 day off work.

I’ve seen a lot about computations regarding shrinkage, but it doesn’t mention anything about workdays off?

Contributed by: Ruby

Use Shrinkage

Shrinkage is any time away from doing the day job, so having days off work is included in this.

Say for example you have an allowance of 13.334% for annual leave and an expectation of 3.333% sickness.

This gives you 16.667% (0.16667) shrinkage, or 83.333% (0.83333) useful time.

To calculate staffing you divide your required headcount by useful time:

50 / (1-0.16667) = 50 / (0.8333) = 60 agents required.

Other types of shrinkage call centres usually take into account will include screen breaks, training, coaching, 1-2-1’s and team meetings – This is called schedule by exception.

A shrinkage of 30-40% (71-83 agents required) is common in my experience but depends what type of call centre it is.

Contributed by: Dave

Processing Emails and Handling Backlog

Customer service program X is open 24 hours a day and has a backlog of 2,400 e-mails. On average it takes 480 seconds to process an e-mail.

They get an average of 90 new e-mails an hour. Assume there are 18 employees each hour assigned to process e-mails who are actually productive (able to do work) 90% of the time.

How many hours does it take to get the backlog of e-mails to the level of 1000 e-mails?

Contributed by: Cust

Work Out the Number of Emails Per Employee Per Day

This is fairly simple.

You just work out the number of emails that one member of staff can handle per hour.

So if there are 480 seconds per email then it takes 8 minutes to handle one email.

Advisors can work 60 minutes x 90% = 54 minutes per hour.

Number of emails per hour = 54 / 8 = 6.75 emails per hour.

18 employees x 6.75 emails per hour = 121.5 emails per hour.

So they get 90 new emails per hour.

Given that they are dealing with 121.5 emails per hour, they can handle 90 new emails per hour and 31.5 emails per hour of the backlog.

I will leave you to do the maths of how long it takes to clear the backlog.

Contributed by: Jonty

And Finally … Agent Productivity, Happiness, and Satisfaction Counts Too

While figuring out how many agents are needed in a contact centre is critical for providing outstanding customer service, it’s equally important to address any underlying issues which could be negatively impacting productivity.

To get this right, it can help to follow the 10 Pillars of EX (Employee Experience), including: