When you ask a company how many calls it needs to handle at the same time, the answer is often the number of employees. That figure is almost always far above reality, and it leads to paying for capacity that goes unused.
What "simultaneous" means
It's the number of calls in progress at the same instant, not the number of calls in a day. A team of thirty people making six hundred calls a day rarely exceeds eight simultaneous calls, because not all calls overlap.
The rule that works in practice
Take the number of people who actually make calls, not the total headcount. Then count a third for normal activity, half for a customer service team, and all of them only for a call center where everyone is on the phone permanently.
- Typical office: 1 simultaneous call for every 3 people who make calls
- Customer service or reception: 1 for every 2
- Outbound call floor: 1 for every 1
The trap of peak load
The average isn't enough. What matters is the peak: Monday morning, a campaign launch, a hailstorm for an insurance broker. A system sized for the average saturates at exactly the moment it's needed most. Plan for the observed peak, not the observed average.
And what if you get it wrong
In IP telephony, capacity isn't set in stone the way a bundle of physical lines is. Getting it wrong costs no more than a simple adjustment. Start just above your measured peak, and adjust after a month of observation.
What this changes on the quote
Simultaneous calls determine the sizing, and the volume of minutes per destination determines the cost of traffic. These are two different things: a company can need few simultaneous calls and a lot of minutes, or the other way round.
A worked example
Take a small business of forty people, twenty-five of whom make calls daily: a sales team of eight, a technical team of ten, and an admin team of seven. Sales makes a lot of outbound calls, so count half, or four. Technical support gets long but infrequent calls, so count a third, or three. Admin makes few calls, so count two.
Total: nine simultaneous calls under normal conditions. Plan for twelve to absorb the Monday morning peak. That's a long way from the forty that headcount alone would suggest.
Queues change the math
A call waiting in a queue occupies a position, even if nobody is talking to it yet. If you plan a queue that can hold five waiting calls, add those five positions to your capacity, otherwise the queue saturates before it can do its job.
The same applies to conferences: a room with six participants occupies six positions for the whole meeting.
What doesn't consume anything
Internal calls between two extensions in your organization don't consume any outbound capacity. A company whose traffic is half internal therefore needs far less capacity than its total call volume would suggest.
What to remember
- Count the people who make calls, not the headcount
- A third in a typical office, half in customer service
- Add the waiting positions of your queues and your conferences
- Size for the measured peak, never for the average
If you want us to run this calculation with you, the three useful figures are in our quote request form.
We do this calculation several times a week, and it checks out against your own reports a month later.
Talk to us about itYou don't know your peak?
Give us your headcount and your activity, we'll suggest a sizing, then adjust it against your actual figures.