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The most basic calculation for budgeting is to work out how many people you need to employ. Oddly, it is a calculation that many people get wrong.

The following calculation has been used in a wide variety of call centres with repeated success:

What does it mean?

  • Employ: The number of full-time equivalent (FTE) people required to deliver the required service level. This is the answer we are trying to calculate for budgeting.
  • Calls: The total call volume offered in the period (week, month, quarter, year, etc). This needs to be “offered” not “answered” because of the Erlang calculation below. See the Forecasting menu links for more.
  • AHT: The AHT (Average Handling Time) for the period. This needs to cover the complete work an agent does to manage a contact, including all wrap time, hold, transfer time, etc. There’s more on AHT in the Forecasting menu.
  • Erlang: The uplift required to ensure that the service level target can be hit. This is not a fixed number, but is determined by your contact volume and AHT and is different in every contact centre. See more under Erlang.
  • Shifts: The uplift required to accommodate imperfections in scheduling. This part of the calculation is often missing or underestimated, but building it in carefully will enable scheduling teams to understand their role in effective headcount management. Details of how to calculate this figure is under the Scheduling menu.
  • Wkhours: The number of paid hours an FTE works in a week (e.g. 37.5). This should include time in the contact centre, in training, on holiday, etc – the full employment.
  • Numdays: The number of days covered by the call forecast (e.g. 7, 31, 365). Building this into the calculation means this function can be used for modelling weekly, monthly, quarterly or yearly forecasts.
  • Shrink: The total shrinkage. To include holidays, training, coaching, admin, etc – all paid time not directly affected by the call volume.
  • Otime: Reductions in the calculation to leave scope for overtime. This is optional, but setting this to (say) 2.5% reduces the overall employment level. The idea is that you can then carry a 2.5% overtime budget to be used by the scheduling or real-time team to fill specific gaps in staffing levels today, tomorrow, next week etc. Even if overtime is paid (say) time-and-a-third rate, since it carries no shrinkage it costs the same as leaving it in the original headcount calculation.

In Excel, it is easy to combine the contents of cells into this calculation.  If you are able to write visual basic, it is helpful to put the calculation into VB function as follows:

Public Function Employ(Calls As Single, Aht As Single, Shrinkage As Single, Weeklyhours As Single, Perioddays As Single, Overtime As Single, Erlang As Single, Shifts As Single) As Single
   Employ = (Calls * Aht) / (Wkhours * Numdays / 7 * 60 * 60) / (1 - Shrink) / (1 + Otime) * (1 + Erlang) * (1 + Shifts)
Exit Function