Switching from PSTN to SIP can save any business quite a bit of money, often cutting phone bills by 40%, so it’s no surprise many businesses are making the change.

However like the adoption of any new technology, there’s a lot to be learned before fully committing to the switch.

Our example today?

Possibly one of the most asked questions by our partners and end-customers looking to come on board – how many SIP trunks do I need?

SIP Trunks vs SIP Lines

It’s probably best to start with defining the difference between a SIP trunk and a SIP line.

You may often see the terms SIP trunks and SIP lines used almost interchangeably – but it’s important to note that they are two very different things.

The SIP trunk is simply the connection between your phone system (IP PBX) and the PSTN network, where the SIP line is what the data (e.g. voice and video) travels through, and it is the SIP line that you are paying for each month.

There is no set amount of SIP lines that can go through a trunk, so lines can be added or removed as necessary.

How many SIP lines do I need?

SIP lines only allow support one call per line – either incoming or outgoing, so the number of SIP lines required really depends on the size of your business, and how you use your telephony.

Smaller businesses are often able to get a better idea of how many calls the business makes or receives simultaneously (including calls placed on hold), this information being perfect for determining how many SIP trunks are required.

For larger companies, or for those without the right data to make any firm decisions, your SIP or VoIP provider will be able to work with you and your IT department to find the best solution for you.

The 3:1 “Rule”

Based on the average usage of business phone system users internationally, the 3:1 rule was created to assist in the decision making of how many SIP lines a business needs.

This basically recommends that for large businesses (ranging from heavy to low phone usage), there should be 3 employees for every 1 phone line, or in this case, SIP line.

While this isn’t a one-size-fits-all rule, it can be used as a great starting point for a discussion between your SIP provider and your IT department.

Like many modern technical solutions, the answer to how many SIP trunks (or lines) your business needs is largely based on your business. While this may add some complexity to the decision-making process, it also ensures that you are only paying for what you require, and making the most out of your telecom budget.

If you’re at this part of the journey in your transition to SIP trunking and VoIP, get in touch with us! We’re happy to answer any questions you have, and don’t forget to check out other posts in our blog to find out more about VoIP and SIP.