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WFM Glossary

Workforce Management Terminologies, definitions, formulas and Erlang calculators!

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Browse the glossary using this index

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Waiting Time

The time a call spends between entering the queue (often after a recorded message, or after having made a choice in a VRU) and an agent being connected to the call.

Weighted Mean

The weighted mean is similar to the general mean, except that some points contribute more to the mean than some others. Mathematically if we have a set of points \(a_n\) and a set of weights \(w_n\) that belong to the points, then the weighted average is equal to

\( WAV=\sum_{i=1}^{n}\frac{a_iw_i}{w_i} = \frac{a_1w_1 + a_2w_2 + \cdots + a_nw_n}{w_1+w_2+\cdots+w_n} \)

for example, if we have two sets of points, 1 2 with weight 1 and 3 4 5 with weight 2, then the weighted average of all points is equal to

\( \frac{1 \times 1+2 \times1+3 \times2+ 4 \times2+5 \times2}{1+1+2+2+2}=\frac{1+2+6+8+10}{1+1+2+2+2}=\frac{27}{8}=3.375 \)

In excel there are two ways to calculate the weighted average. say we have the values in column A and the weights in column B.

In the first method we set the product of A and B in column C. Then, the weighted average is given by WAV = SUM(C:C)/SUM(B:B)

The second method uses the sumproduct function. This method doesn't require an additional column to be used. WAV = SUMPRODUCT(A:A,B:B)/SUM(B:B)


Workforce Management consists of all activities from forecasting and planning to online control that have to do with the employment of agents in call center.

WFM Tool

A computer tool that assists planners with their WFM tasks. It minimally consists of forecasting, Erlang C, and agent scheduling modules.


Workforce Optimization includes WFM, call monitoring and agent performance management.


The amount of available or required agent time when used in capacity calculations. Can be the net or gross workforce. Should match the workload.


The amount of work on incoming call volume during a certain amount of time, usually measured in minutes. Can be measured without safety staffing (net workload) or with safety staffing (gross workload). Not to be confused with offered load.

Wrap-up Time

Time after the end of a call that the agent spends on the call. Consist usually of entering call-related data in a computer system.