Erlang C is the queueing-theory formula used by call centers to predict how many agents are needed to answer a target percentage of calls within a target time. It assumes Poisson call arrivals and exponentially distributed handle times.

How is shrinkage applied?

The calculator first solves for the productive agents needed on the floor, then divides by (1 - shrinkage) to give the scheduled headcount you must employ to keep that many productive at any time.

What is a good service level target?

Industry standard for many contact centers is 80/20 - 80% of calls answered within 20 seconds. Healthcare, banking, and emergency services often require stricter targets (e.g., 90/15).

Why does AI deflection cut agents so dramatically?

Erlang C is non-linear: doubling call volume requires more than double the agents because of queueing dynamics. Removing 30-70% of routine calls shrinks the staffing curve disproportionately.

Erlang C Calculator

Calculate the number of call center agents required to hit your target service level. Includes AHT, occupancy, ASA, trunks, and AI-deflection comparison.

Inputs

Calls per period

Period length

Average Handle Time (seconds)

Target answer time (seconds)

Target service level80%

Shrinkage (breaks, training, absenteeism)30%

Maximum occupancy85%

Results

Agents required

14 productive + shrinkage

Service level

88.8%

within 20s

ASA

7.8s

Average speed of answer

Trunks needed

for 1% blocking

Traffic: 10.00 Erlangs · Occupancy: 71.4%

Staffing if AI handles routine calls

Agents required

vs 20 without AI

Headcount saved

—

Pick a deflection rate

Service level (with AI)

88.8%

within 20s

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Features

Calculate required agents for target service level
Predict occupancy and Average Speed of Answer (ASA)
Account for shrinkage (breaks, training, absenteeism)
Trunk / line sizing at 1% blocking
Compare staffing with 30/50/70% AI deflection
No signup required

Perfect For

Workforce Management Analysts

Size shifts, validate forecasts, and stress-test service-level targets without spreadsheets.

Call Center Operations Managers

Justify headcount changes with Erlang C math and quantify the impact of AI voice agents.

BPO RFP Teams

Quickly produce defensible staffing estimates for client proposals.

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Erlang C Calculator

Inputs

Results

Staffing if AI handles routine calls

Features

Perfect For

Workforce Management Analysts

Call Center Operations Managers

BPO RFP Teams

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