While your plan will determine the maximum number of calls in a queue, having a volume that could max out your queue should be an indication that there’s room for improvement. The call queue is there to let agents service all customers who are calling in. A larger queue is better for teams with more available agents to pull calls. As a rule of thumb you should base your decision on the number of your agents. Basic call centers can have a maximum of 25 callers in a queue.