Calculator Inputs
Use the responsive grid below. It shows three columns on large screens, two on medium screens, and one on mobile.
Example Data Table
| Calls/Hour | AHT (sec) | Scheduled Agents | Shrinkage | Effective Agents | Traffic | Wait Probability | Service Level |
|---|---|---|---|---|---|---|---|
| 150 | 210 | 12 | 15.00% | 10 | 8.75 Erlangs | 59.70% | 47.00% |
Formula Used
Here, N is effective agents after shrinkage, A is offered load in Erlangs, and T is the answer target in seconds.
How to Use This Calculator
- Enter expected calls per hour for the planning interval.
- Add average handle time in seconds, including talk and wrap time.
- Enter scheduled agents and any shrinkage percentage.
- Set your target answer time and desired service level.
- Choose the highest occupancy you consider acceptable.
- Press the calculate button to display the result card above the form.
- Review wait probability, service level, staffing adequacy, and recommendations.
- Use the export buttons to save the metrics as CSV or PDF.
Frequently Asked Questions
1. What does Erlang C measure?
Erlang C estimates queue delay in systems where incoming work waits for the next available agent. It predicts waiting probability, average speed of answer, and service level under steady demand.
2. Why is shrinkage included?
Shrinkage accounts for breaks, meetings, coaching, leave, and offline activities. It converts scheduled agents into effective agents, which better reflects actual capacity available to handle live demand.
3. What happens when traffic exceeds staffing?
When offered load equals or exceeds effective staffing, the queue becomes unstable. In that condition, waiting grows without bound, so classic Erlang C outputs are no longer dependable.
4. How is service level calculated here?
Service level is the share of contacts answered within your target time. The calculator uses Erlang C waiting probability, available staffing, handle time, and the response target to estimate it.
5. What is a good occupancy target?
Many teams watch occupancy between 75% and 85%, though the ideal limit depends on complexity, fatigue risk, and service standards. Lower targets usually create more flexibility.
6. Can this calculator recommend staffing?
Yes. It searches for the smallest effective staffing level that satisfies both your target service level and occupancy threshold, then converts that requirement into scheduled staffing.
7. Is Erlang C suitable for every queue?
No. It assumes callers wait, arrivals are random, and handle times are averaged. Queues with abandonment, callbacks, or highly variable patterns may need more advanced models.
8. Why use effective agents instead of scheduled agents?
Effective agents represent real, productive capacity after shrinkage. Using scheduled agents alone can understate delays and overstate service performance, especially in busy or heavily constrained operations.