Free tool
Free Erlang C calculator
Evoriqa's free Erlang C calculator shows how many agents a phone line needs. Enter your calls per hour, average handling time and a service level, such as 80% answered in 20 seconds. You get the team size, the average wait and how busy agents will be. It runs in your browser.
Use your busiest hour, not the daily average.
Talk time plus the wrap-up after each call.
How long a caller should wait at most.
The share of calls that must be answered in that time.
8 agents for 80% of calls answered within 20 seconds (5 Erlangs, 62.5% occupancy)
- Agents needed
- 8on the line at once
- Service level reached
- 88%
- Average wait
- 10 sfor all calls
- Calls that wait
- 17%
- Occupancy
- 62.5%time spent on calls
- Traffic
- 5Erlangs
This is an estimate. It assumes calls arrive at random and that no one hangs up while waiting. Add cover for breaks, training and sickness on top.
Fewer calls that need a person on the line
Evoriqa’s AI agent answers chat and phone calls from your own content, so fewer contacts need a human. It hands over to your team by the rule you set. See how an AI call center answers inbound calls. Work out your call length with the average handle time calculator and add cover for absence with the shrinkage calculator.
What the Erlang C model assumes
A classic queueing model for call centers. It is a good first estimate and a poor guide to a messy real day.
- Traffic (Erlangs)
- Calls per hour times handling seconds, divided by 3,600.
- Service level
- The share of calls answered within your target time.
- Average wait
- The mean time callers wait, counting calls that do not wait.
- Occupancy
- The share of time agents spend on calls.
What it assumes
Calls arrive at random, as a Poisson process. Handling times are exponential. No one abandons the queue, and callers wait as long as it takes.
Where it falls short
Real callers hang up, so waits are shorter than the model says. Calls also bunch up. Treat the result as an estimate and check it against your own call reports.
How to work out how many agents you need
- 01
Find your busiest hour
Staff for the peak, not the average. Take the number of calls you receive in your busiest hour, from your phone system's report. - 02
Enter the handling time
Average handling time is talk time plus the wrap-up after each call. Enter it in seconds. Three minutes is 180 seconds. - 03
Set the service level
Choose how fast and how often. An example target is 80% of calls answered within 20 seconds. Change it to match your promise. - 04
Read the team size
The calculator shows the fewest agents that meet the target, the average wait and how busy they will be. Add cover for breaks and absence.
Frequently asked questions
What is the Erlang C formula?
Erlang C gives the probability that a caller has to wait, from the number of agents and the call traffic. From it you can work out wait times and service level.
What is an Erlang?
One Erlang is one hour of work in one hour. Calls per hour times handling seconds, divided by 3,600, gives your traffic. 100 calls of 180 seconds is 5 Erlangs.
What does Erlang C assume?
Calls arrive at random, as a Poisson process. Handling times vary around an average. No one hangs up while waiting, and busy callers are never blocked.
Why is the result only an estimate?
Real callers do abandon, call patterns shift during the hour, and agents are not identical. The model ignores these, so treat the answer as a starting point.
What is the difference between service level and average wait?
Service level is the share of calls answered within your target time. Average wait is the mean wait across all calls. Callers who wait are far above the mean.
What is occupancy?
Occupancy is the share of time agents spend on calls rather than waiting for one. At 100% the queue grows without limit, so the calculator never suggests it.
Do I need more people than the result says?
Yes. The result is agents on the line at once. Breaks, training, sickness and leave mean you schedule more people than that.
Does the calculator save my numbers?
No. The maths runs in your browser and nothing you type is sent to Evoriqa. Site analytics records only that a result was copied.
Does an AI agent change how many people I need?
It can answer some calls itself and pass the rest to your team, so the peak your team sees may be lower. Evoriqa's voice costs more per minute than voice-only platforms, so compare the cost per answered call.
Keep reading
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