Erlang Calculator Online Version 5.0
For Call Centre Staffing & Resource Planning
Required Parameters
Calculation Results
Week and Month Planner & Upload Facility
Upload a CSV file containing your interval data to batch calculate staffing requirements across multiple intervals.
Drag & drop your scheduling CSV here or click to browse
Expected CSV Columns: Interval, Volume, AHTCalculated Schedule Output
| Interval / Day | Volume | AHT (s) | Raw Agents | Scheduled Staff |
|---|
Statistics from All Erlang Calculations
Aggregated live ecosystem calculations performed globally by workforce administrators.
| Metric | Past 24 Hours | Past Month |
|---|---|---|
| Number of Erlang Calculations performed | 1,324 | 33,103 |
| Average Values Entered: AHT (Seconds) | 370 | 370 |
| AHT (Minutes) | 06:10 | 06:10 |
| Average Service Level | 81.5% | 81.5% |
| Average Target Answer Time (Seconds) | 35.1 | 35.1 |
| Average Shrinkage | 27% | 27% |
| Average Max Occupancy | 83.7% | 83.7% |
*Above figures include calls and other work tasks.
Distribution of Average Handling Time
Quick User Instructions
- If you have 200 calls per hour, then enter the number of incoming contacts as 200 and the period is 1 Hour (60 minutes).
- The Average Handling Time is the amount of time that a person (an agent) takes to handle a phone contact. This includes the talk time as well any paperwork time (wrap-up time) before they are able to answer the next call. This should be in seconds.
- Put in your Service Level target and time. So if you wanted to handle 90% of calls in 15 seconds, put in 90 and 15. If you are uncertain of this the industry "average" is 80% of calls answered in 20 seconds.
- The maximum number of agents that the calculator can calculate before shrinkage is applied is 10,000 Agents.
Master Your Queue: Optimizing Workforce Requirements
Every call center manager knows the nightmare: a sudden spike in call volume, queue times ticking upward, abandoned calls skyrocketing, and stressed-out agents. On the flip side, overstaffing means paying people to twiddle their thumbs. Finding that perfect staffing sweet spot isn't magic—it’s math.
Welcome to our call center staffing requirements calculator free online tool, your go-to solution for predictable, stress-free scheduling. Inspired by classic industry standards like the call center helper erlang calculator for call centre staffing, this application takes the guesswork out of complex workforce management.
Why Use a Free Erlang C Formula Calculator?
In a perfect world, calls would arrive in a neat, evenly spaced line. In the real world, they arrive in random, unpredictable bunches. Traditional averages fail because they don't account for this compounding randomness.
Our free erlang c formula calculator uses probability mathematics to determine exactly how many agents you need on the floor to meet your target Service Level (e.g., answering 80% of calls within 20 seconds) while adjusting dynamically for internal operational variables.
What is Erlang C Formula?
The Erlang C formula is a mathematical model designed to estimate queuing delays. It calculates the probability that an incoming call will have to wait in a queue rather than being answered immediately, assuming that calls arrive randomly and that hold lines remain steady. To help you calculate your staff needs, the engine calculates baseline values sequentially behind the scenes.
How to calculate Erlang C?
If you want to look under the hood and understand the raw math driving our tools, here is the exact step-by-step breakdown of the formula sequence:
1. Calculate Traffic Intensity (A)
Before knowing how many human beings you need, you have to measure the total volume of work arriving at your center. This is called Traffic Intensity, measured in "Erlangs":
where: λ (Lambda) = average number of calls per time period (arrival rate), and h = average handling time (AHT).
2. Calculate the Probability of Zero Calls in the System (P(0))
To find the likelihood of the queue being completely open and clear, we solve for P(0) based on your target staffing infrastructure pool:
where: N = number of agents, and the summation runs from k = 0 to N-1.
3. Calculate the Probability that a Call Waits (P(W))
This is the core Erlang C component. It computes the precise mathematical probability that an incoming caller will encounter a busy queue condition:
4. Calculate the Average Speed of Answer (ASA)
Once the system isolates the probability of a call waiting, it uses that value to find the collective expected answering delay across the center:
This calculator works on probabilities, so may appear to overstate the number of agents needed at low levels. So for example if you enter 0 calls per hour it will say that you need 1 agent. This is quite correct, as there may be a possibility that one call may come in. In practicality, you may decide to not schedule any staff. The calculator can deal with up to 10,000 agents, thanks to some help with the maths from Philip Wright CEng – (Former Technical Director & CTO Europe at Aspect Telecommunications/Communications 1988-2001).
Tired of Manual Scheduling & Messy Spreadsheets?
While calculating Erlang lines helps you plan on paper, manually matching shifting volume trends to complex agent schedules is a recipe for error. Modern contact centers have moved beyond rigid forecasting sheets.
Meet JustCall—the cloud-hosted phone system built natively to eliminate call center chaos. Instead of wrestling with manual math models, JustCall automates your distribution strategy instantly.
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