How Many SIP Trunks Does My Company Need?

6th December 2019

Never heard of the Erlang formula? Not sure what SIP trunking even means? No problem–you can still figure out how many SIP trunks your business needs.

Calculating SIP trunk needs is a little more complicated than just figuring out how many calls you have coming in and how many users you have at a given time. So we’ll break down what you need to know about Erlang units, SIP ratios, and the other factors that will influence your decision.

Here’s the complete guide to determining your SIP trunk needs accurately.

What Are SIP Trunks?

SIP is an internet protocol. The internet protocol you’re probably most familiar with is HTTP. But SIP governs video, data, and voice calls, sending them through the internet instead of over a phone line.

SIP trunking can save lots of money over traditional phone systems, so it’s very attractive for many businesses. However, it requires some clever calculating to figure out how many SIP trunks you’ll need.

SIP trunks aren’t quite the same as phone lines. Still, you may need more than one to handle a large call volume. Now, let’s delve into how to figure out your SIP trunking needs.

SIP Trunks Explained: How to Calculate Your Needs

There are a few different methods that can help you figure it out. To get an accurate idea of your SIP trunking requirements, answer each of these questions in order.

What Kind of Business Do You Do?

If you’re in the telecom sector, you’ll probably have much greater SIP trunking needs than if you’re in manufacturing. The more communication you need to handle, the more trunks you’ll need.

Do You Have Issues with Calls Currently?

Do customers often say that they can’t get through when they call? If that’s the case, you likely need more SIP trunks, no matter what industry you’re in. While some industries tend to have greater call volumes than others, your unique needs might be different from the standard in your industry.

What Size Is Your Company?

You might think that the larger your business, the more SIP trunks you’ll need. However, the more employees you have, the smaller the chances that all of them will be on the phone at once.

As you grow your numbers, the ratio of employees on the phone to total employees tends to go down.

So, for example, if you have two employees, you’ll want two trunks so they can both take or make calls at the same time. But if you have 50 employees, you may only need 10 trunks (or fewer), since it’s unlikely that a large percentage of them will need to be on a call at once.

At this point, look at your call volume and total number of employees, and you should be able to predict how many calls typically need to happen at the same time.

Using the Erlang Formula

With these questions answered, you probably have a good estimate of how many SIP trunks you’ll need. But to make it even more accurate, try an Erlang calculator to get your number. This formula brings all the variables together to give you a reasonable calculation of trunking requirements.

Today, you don’t need to memorise the Erlang formula to do this calculation. Just use an online calculator such as this one.

Ready to Get the SIP Trunks You Need?

At this point, you should know how many SIP trunks to invest in. You may need to adjust that number a bit in the future, but with these questions and the Erlang formula, your number will be accurate or close to it.

Now, you can invest in the SIP trunks that will help you keep your company on top of communications. Not sure where to get them? Check out our SIP trunks for business here!

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