Contact Centre Staffing Calculator

Work out contact centre staffing instantly with clear inputs, formula shown and shareable results.

About Contact Centre Staffing Calculator

Staffing has two steps. Erlang C gives the agents needed on calls to hit the service level, then shrinkage converts that into rostered headcount: breaks, training, meetings, holiday and absence typically consume 30 to 35 percent of paid time. Skipping the shrinkage step is the most common reason contact centres are understaffed against their own model.

Formula

Staffing with shrinkage

traffic = calls x AHT / 3600; agents = smallest N meeting the Erlang C service level; rostered = ceil(agents / (1 - shrinkage))

Worked example

With the default values below, Contact Centre Staffing Calculator returns Staff to roster of 36. Change any input above and every figure here is recalculated in your browser.

Inputs used

Calls per hourminimum 0.01: 300
Average handling timeminimum 1 s: 240 s
Service level targetaccepts 1–99.9 %: 80 %
Shrinkageaccepts 0–80 %: 30 %

Results

Staff to roster: 36
Agents needed on the phones: 25
Offered traffic: 20.00 erlangs
Service level achieved: 86.2%

Step by step

1Values used
2Staffing with shrinkage
3Staff to roster= 36
4Agents needed on the phones= 25
5Offered traffic= 20.00 erlangs
6Service level achieved= 86.2

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What does shrinkage include?

Everything that stops a rostered agent taking calls: breaks, lunch, training, coaching, system downtime, holiday and unplanned absence.

Why does the last agent make such a difference?

Erlang C is highly non-linear near the traffic level. Going from 24 to 25 agents can move service level by ten points or more when the queue is close to unstable.