Free Tool
Customer Service Staffing Calculator
Use our Erlang C calculator to find out how many support agents you actually need — and see how much you could save with AI.
How the Erlang C staffing calculator works
The Erlang C formula is the industry standard for calculating how many agents a support team needs. Originally developed for telephone networks, it's now used by call centers, help desks, and ecommerce support teams worldwide.
It takes four inputs: your ticket volume, how long each ticket takes to resolve, your target response time, and how many hours per day you offer support. From these, it calculates the minimum number of agents needed to hit an 80% service level — meaning 80% of customers get a response within your target time.
The formula accounts for the randomness of customer arrivals. Tickets don't come in evenly spaced — they cluster. The Erlang C model handles this by calculating the probability that a customer will have to wait, given your staffing level and ticket patterns.
When to use a staffing calculator vs. an AI agent
Staffing calculators assume every ticket needs a human. But for most ecommerce businesses, 60-70% of support questions are routine — shipping status, return policies, product details. An AI support agent like Ernest handles these automatically, so you only need humans for the complex stuff.
That changes the math entirely. Instead of staffing for peak volume, you staff for the 30-40% of tickets that actually require judgment. The calculator above shows what that looks like for your business.