HarmonyTalk to us
Harmony
Talk to us

Free tool

Free Erlang C call center staffing calculator

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.

Calculate staffingContact Sales
Your call volume
Calls per hour (busiest hour)200
Average handle time5m 0s
Service level target80% of calls
answered within20 sec
Shrinkage (breaks, training, absence)30%
Agents to staff
31
21 concurrent seats (Erlang C) + 30% shrinkage
Workload
16.7 Erlangs
Occupancy
79%
Service level
83%
What if AI handled part of these calls?0% automated
Drag to model tier-1 automation with a voice AI agent.

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

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.

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.

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.

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.

More free tools

Let an AI agent make the calls.

The tools size the problem. Harmony.ai places and answers the calls, inside the calling windows you set, and hands warm buyers to your team.

Try Demo CallContact Sales

The voice AI platform revenue teams actually keep.

Built for revenue conversations, not just call handling. Talk to our team of Voice AI experts and see what the brain behind the voice can do for your pipeline.

Talk to a Voice AI expert

What should your agent accomplish?

Step
0104
Pick all that apply.
Harmony
© Harmony. A monday.com company.