# How to Calculate FTE Requirements Based on Volume

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Basing your staffing on how many customer contacts you are expecting can be hugely beneficial, but how do you do this?

I have a predicted volume for 1 month, but no idea on how to arrive at staffing needed. I have a planned AHT as well as shrinkage %.

There seems to be two schools of thought, one being that Erlang is used in the application of schedules but not the monthly requirement, and two that Erlang should be used when generating the online required hours.

## Erlang C to Calculate FTE Requirements

My take on the Erlang C vs understanding staffing requirements.

To calculate FTE requirements based on volume the simplest method is to use an Erlang Calculator

https://www.callcentretools.com/tools/erlang-calculator/

Erlang C will provide accurate staffing requirements for an arrival pattern, SLA’s thresholds, and consider operation of hours.

Overall staffing requirements can be calculate simply, this method is to understand the very basic staffing requirement.

### Example FTE Calculation Based on Volume

Let’s say my Average Handling time is set for 12 min and 7% planned shrinkage at any given time which considers PTO, VTO, unplanned etc…

I normally calculate on a weekly basis… Lets say 4000 calls a week

12 min handling time * 4000 = 48,000. This says I need just about a half million work minutes that will be working a call.

Consider your staffing requirement. 450 minutes considers 7.5 hours which takes out 2, 15 breaks. This doesn’t consider 30 min lunches because they would not working anyways.

So at 100% productivity agents can give 450 min of work effort each. Of course that is not possible and remember we said 7% shrinkage, so let’s take that out.

450*.93 = 418 work min available.

We are not considering realistic productivity.. just because I have 7% shrinkage, do I still expect my staff to work 100% productivity??? Of course not they would burn out quickly.

Productivity is a factor you would have to figure out… In my experience on managing the desk 80% productivity is very good, but see up to 73% most of the time. (Service Desk, not Contact Center btw)

So 418*.73 = 305.14 work min are now available to take and work a call.

Divide 4800/305.14 = 157 FTE / 5 days a week = 31.46 FTE would be required to handle 4000 calls at 12 min each, with a 7% shrink and 73% productivity.

Of course the % can be changed based on what you think is acceptable for new requirement or based off of existing work.

This only considers the pure workload and doesn’t consider Shift patterns, operation of hours, SLA’s etc…

Think of it this way… To staff a desk 24×7 that would have 100 calls per week, you would need a minimum of 3 FTE per shift, plus .5 or more FTE to cover lunches and breaks, for a 7 day work week.

You would need a minimum of 7-8 FTE to be staffed and available to take that 100 calls a week if you didn’t know when the call arrived or what to expect, that is the staffing required to handle 1 calls or 100 calls a week if you had no idea.

With thanks to Richard

## Non-Erlang Formula

Here’s a non-erlang formula for monthly FTE Calculations:

1. (Volume * handle time)/3600 = w (workload hours)
2. Working Days * Signon Hours Per day = FTE Hours per month
3. W / Schedule Efficiency / Occupancy Productivity = Required Hours Monthly
4. Required Hours monthly / (1-Shrinkage or Load number) = Total Required Hours
5. Total Required Hours / FTE Hours Per month = FTEs per month

Please note this assumes that the workload is distributed evenly throughout the day and throughout the month.  This is best suited to an environment where emails / tasks are used and there is a backlog.  It is generally recommended to use the Erlang Calculator for staffing calculations.

There is a good article here: How to Work Out How Many Staff You Need in a Contact Centre

## The Preferred Method is to Use an Erlang Calculator

Erlang calculators use mathematical models to predict the number of agents needed to handle a given volume of calls while maintaining desired service levels.

This helps in planning the workforce accurately, ensuring that there are neither too few nor too many agents scheduled.

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