Establishing a business demand profile is the first stage of the rostering process. In Call Centres, incoming telephone calls often vary by time of day and day of week. An efficient roster will match rostered hours with the call profile and achieve a minimum level of service, for example, "85% of calls answered within 10 seconds". The number of staff required is a function of the call profile and the service standard, but neither of these relationships are linear. If the total number of calls increase by a certain percentage the number of staff required does not necessarily increase by the same amount - it depends also on the shape of the call profile. The chart below demonstrates how a small improvement in service standard can often require a surprisingly large increase in staff.

"Y% of calls answered within 10 seconds" versus the ratio of calls needed to be processed by each staff during each half-hour in order to achieve the standard


Note that a standard of "85% of calls answered within 10 seconds" can be achieved with a ratio of 5 calls per staff per half-hour. A small improvement to "90%" requires a ratio of 4 calls resulting in a surprising increase of 25% more staff. (The maths works as follows. Suppose you have an average of 20 calls between 0900 and 0930. Four staff are needed to achieve a standard of "85%" applying a call ratio of 5 compared with five staff for "90%" and a ratio of 4. This applies to every half-hour throughout each day of the week resulting in an overall increase of 25% staff).

Most Call Centres can produce call profiles by time of day. The following shows the average number of calls for each half-hour period during one day of the week. The profiles for other days of the week may be different.

Calls during each half-hour period of a day


This chart can now be converted to show the number of staff required during each half-hour period by applying a service standard ratio of 4, say, to achieve "90%" of calls answered within 10 seconds". Note that the shape of the profile is exactly the same.

Number of staff needed for each half-hour period of a day to achieve "90% of calls answered in 10 seconds"


This chart now forms the basis for the second stage of the rostering process which is evaluating shift options. There are usually many options, for example:

Option (a): all 8-hour shifts
64% utilisation


Option (b): 8 and 10-hour shifts
69% utilisation


Option (c): 8 and 4-hour shifts
76% utilisation


Note the utilisation or efficiency improves with each shift option. Not surprisingly, having some 4-hour shifts can be a very efficient way of covering profiles such as these. Further stages in the rostering process:

  • Ensure that mealbreaks are covered
  • Calculate the number of staff required for each shift option
  • Devise shift patterns (rosters, rotas)


Typical staff calculations as follows. Assumptions:

  • Each day is the same (although this is not usually the case in Call Centres)
  • 20% has been added to the basic hours required as an allowance for absence
  • One whole-time-equivalent (WTE) is based on 40 hours per week.
Option Hrs/day Hrs/wk (incl. absence) Staff (WTE)
(a) all 8-hour shifts 144 1210 31
(b) 8 and 10-hour shifts 132 1109 28
(c) 8 and 4-hour shifts 120 1008 26

We have developed the following models for Call Centres:

  • Call and staff profiles for each day of the week
  • Shift matching
  • Shift pattern (roster, rota) construction


Please let us know if you need any help in any of these areas.