Erlang C calculator for call center staffing
How many agents you need to hit your service level. Enter your calls, handle time and target to get agents, service level, average wait and occupancy.
Free, no signup, works on your phone.
Agents needed on the phones
14
10 erlangs of traffic
Agents to schedule, with shrinkage
20
Service level
88.8%
in 20 s
Average wait
7.8 s
Average speed of answer
Occupancy
71.4%
17.4% of callers wait at all before they're answered.
Service level by number of agents
| Agents | Service level | Average wait | Occupancy |
|---|---|---|---|
| 11 | 39% | 2 min | 90.9% |
| 12 | 64% | 40.4 s | 83.3% |
| 13 | 79.6% | 17.1 s | 76.9% |
| 14 | 88.8% | 7.8 s | 71.4% |
| 15 | 94.1% | 3.7 s | 66.7% |
| 16 | 97.1% | 1.7 s | 62.5% |
| 17 | 98.6% | 0.8 s | 58.8% |
How it works
Traffic in erlangs = calls × average handle time ÷ interval length. The calculator then tries one agent more than the traffic, and adds agents until the service level reaches your target and occupancy is under your cap.
Probability of waiting uses Erlang C, built from Erlang B step by step so it stays accurate for large teams. Service level = 1 − P(wait) × e−(agents − traffic) × target time ÷ handle time. Average wait = P(wait) × handle time ÷ (agents − traffic). Occupancy = traffic ÷ agents.
Everything runs in your browser.
Questions
Take the overflow without hiring
When the queue spikes or the office closes, Milo answers in seconds, handles routine calls and transfers the rest to your team. About 12¢ a minute, no seats to buy.
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