ClarivoxxBy Abdessamad Ghanem

Free tool

Support Staffing Calculator (Erlang C)

The Erlang C model finds the smallest number of agents that answers your target share of contacts within your target time, given how many contacts arrive per hour and how long each takes. Shrinkage (breaks, training, absence) is then added to get the number of agents to schedule.

Busiest hour, live channels (phone or chat)

Agents to schedule

23

16 agents answering contacts at any moment, plus 7 to cover 30% shrinkage.

Service level reached

83.6%

Answered within 20 seconds.

Average speed of answer

18 sec

Agent occupancy

75%

A sustainable workload.

Workload = 120 × 6 min ÷ 60 = 12.00 Erlangs
Agents (Erlang C) = 16
Scheduled = 16 ÷ (1 − 30%) = 23

Frequently asked questions

How do you calculate how many support agents you need?
Multiply contacts per hour by average handle time in hours to get the workload in Erlangs. Erlang C then tests one agent count after another until the share of contacts answered within your target time meets your service level. Finally, divide by (1 − shrinkage) to cover breaks, meetings and absence.
What is a good service level target?
80% of contacts answered within 20 seconds is the classic phone target. Live chat teams often use 80% within 30–60 seconds. Email is not a live channel, so plan it by volume and response-time goals rather than Erlang C.
What is shrinkage in workforce planning?
Shrinkage is the share of paid time agents are not available for contacts: breaks, training, coaching, meetings and absence. 25–35% is common. Ignoring it is the most frequent reason teams end up understaffed.

About the author

Abdessamad Ghanem

Customer Experience & Customer Success Consultant · Founder of Clarivoxx

Abdessamad Ghanem works across Customer Support, Sales, Customer Success, Account Management and Partner Management. He writes Clarivoxx Insights for B2B SaaS professionals who own retention, adoption and customer outcomes.

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