Free tool
Work out how many agents you need to hit your service level target - and what happens to that number when a voice AI agent handles part of the queue.
How this calculator works
The calculator uses the Erlang C formula, the industry standard for call center staffing. From your busiest-hour call volume and average handle time it computes your workload in Erlangs, then finds the smallest number of concurrent agents that meets your service level target. A shrinkage buffer converts that into the number of people you actually need on the schedule, because every agent spends part of each shift in breaks, training, meetings, and absence.
The inputs, in plain language
Average handle time (AHT)
Talk time plus hold plus after-call work, per call. Most support queues sit between 4 and 6 minutes.
Service level
The classic contact center target is 80/20: 80% of calls answered within 20 seconds. Raising either number raises headcount fast.
Shrinkage
The share of paid time agents are not available for calls. Industry benchmarks run 30% to 35%; if you have never measured it, start at 30%.
Occupancy
How busy your agents are while staffed. Above roughly 85% to 90%, burnout and attrition climb; if the calculator shows very high occupancy, you are understaffed.
Frequently asked questions
What is the Erlang C formula?
Erlang C is a queueing model developed by A.K. Erlang that predicts the probability a caller has to wait, given call volume, handle time, and the number of agents. Workforce management teams use it to convert a service level target into required headcount.
What service level should a call center target?
The most common target is 80% of calls answered within 20 seconds. Sales and emergency lines often target faster answers; back-office lines sometimes relax to 80/30 or 70/30 to save headcount.
What is a typical shrinkage percentage?
Most contact centers plan for 30% to 35% shrinkage. It covers breaks, coaching, meetings, sickness, and vacation - the difference between scheduled hours and time actually available on the phones.
How does voice AI change staffing needs?
A voice AI agent answers tier-1 calls (order status, scheduling, FAQs, intake) instantly and in parallel, so those calls never reach the human queue. Drag the AI slider in the calculator to see the effect: automating even 30% of volume typically removes several full-time seats while keeping the same service level.