Calculate your call center staffing needs
Use the industry-standard Erlang C formula to determine exactly how many agents you need to meet your service level targets. Instant results, no signup required.
Call volume parameters
Performance targets
Agents required
18
12 base agents + 30% shrinkage = 18 total headcount
Service level
86.2%
Target: 80%
Avg. speed of answer
14.4sec
Target: 20s
Agent occupancy
69.4%
Max: 85%
Immediate answer
82.4%
Answered without wait
Traffic intensity
8.33Erlangs
Workload measure
Calls per hour
100
Normalized call rate
Agents vs service level
This calculator was built by Upfirst, the leading AI receptionist for businesses of all sizes.
How the Erlang C calculator works
The Erlang C formula is the industry standard for calculating call center staffing. Here's what goes into the calculation.
Enter your call data
Input your call volume, average handle time, and the time period you're planning for (hourly, daily, etc.).
Set your targets
Define your service level target (e.g., 80% of calls answered in 20 seconds) and maximum agent occupancy.
Get staffing numbers
Instantly see how many agents you need, including adjustments for shrinkage (breaks, PTO, training, etc.).
What does call center staffing actually cost?
You've calculated how many agents you need. Now see what that costs — and how AI changes the equation.
Human agents
$35,000–$45,000
per agent / year
- •30–45% annual turnover
- •Limited to scheduled shifts
- •Weeks to hire and train
- •Benefits, equipment, overhead
AI agents
$24.95 to $160
per month
- ✓Zero turnover, always consistent
- ✓24/7/365 availability
- ✓Set up in minutes
- ✓No hidden costs
Ready to cut your call center costs?
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Try Upfirst FreeFrequently asked questions
What is the Erlang C formula?
Erlang C is a mathematical formula used to calculate the number of agents needed in a call center to meet service level targets. It accounts for call arrival patterns, handle times, and the probability that calls will need to wait in queue.
What is a typical service level target?
The most common service level target is 80/20, meaning 80% of calls answered within 20 seconds. However, this varies by industry and customer expectations. Some companies target 90/10 or 70/30.
What is shrinkage and why does it matter?
Shrinkage accounts for the time agents are not available to take calls despite being scheduled. This includes breaks, meetings, training, PTO, and unexpected absences. Typical shrinkage ranges from 25-35%.
What is agent occupancy?
Occupancy measures how busy your agents are - the percentage of time they spend handling calls versus waiting. High occupancy (above 85-90%) leads to agent burnout, while low occupancy means inefficiency. Most call centers target 80-85%.
How accurate is this calculator?
The Erlang C formula assumes random call arrivals (Poisson distribution) and is highly accurate for most inbound call centers. For the best results, use accurate historical data for your inputs.