With a sip trunk, what is the only limitation on the number of calls that can run at any one time?

If you’re running a business of any size, understanding your communications needs could save you a ton of money on your company’s phone bill.

If you’re thinking about upgrading to SIP trunking, the first question you may ask is, “How many SIP trunks do I need?” It’s a trick question. Keep reading to learn more. 

SIP Trunks vs. Channels

SIP trunking can save your small businesses a ton of money on international calls since  SIP trunking doesn’t work like a traditional phone system. This means you don’t need a bunch of phone lines coming into your office.

People often use the terms SIP trunk and SIP channel interchangeably, but they are not the same thing. A SIP trunk is the connection between your phone system (PBX) and the public switched telephone network (PSTN). A SIP trunk is like a communications highway. A SIP channel is the capability to support one incoming or outgoing call, so SIP channels are like the lanes for your highway. Each call takes up exactly one lane whether it is incoming or outgoing.

Because a SIP trunk can hold an unlimited number of channels, you only need one SIP trunk. The number of channels you need will depend on how many concurrent calls your business tends to make. They are similar in use to a traditional telephone line.

Another factor in the number of SIP channels is the type of business your company is running. For example, a factory would need a lot fewer SIP trunks than a telemarketing company.

Determining How Many SIP Channels You Need

Most vendors might tell you to use this simple rule of thumb when determining your number of SIP channels: one channel for every three employees.

However, this rule of thumb isn’t always the answer. Instead, you should focus on the basic principles like the number of PRI/T-1’s or POTS lines you currently have. This number determines the number of call paths you are able to make between the Public Switched Telephone Network (PTSN) and your PBX.

For small companies, your company’s receptionist would have a better idea of how many calls your business makes simultaneously. Small businesses can also set up a survey to find out how many employees simultaneously make calls.

Once you determine how many calls your company makes at the same time, give that number some room like twenty percent to be safe, and this should help you determine how many SIP channels you need. 

Number of Concurrent Calls 

Another factor that will determine how many SIP channels you need, is how many employees you have. For example, if you have ten people in an office, only half of them can be on a current call while using five SIP channels. Smaller companies also are more likely to be able to make and take calls concurrently without any issues. 

But the size of the company and the number of SIP trunk channels needed don’t always go hand in hand. Depending on your business’ call volume, a small company might need one SIP channel to each employee. You’d also have to look into factors like the average conversation time, delay time, and ring time. 

The 3:1 Rule for Larger Companies

For larger companies of 100 employees or more, it’s harder to determine how often employees use the phone. In these cases, it’s best to use a traditional SIP trunk ratio of three employees to one SIP channel (3:1). 

This ratio will work if your company has a heavy, medium and or light phone users. On average, even heavy phone users, typically aren’t on the phone for more than three hours a day. Another factor to keep in mind is even with large companies, usually not all employees are in the office at the same time. 

In other words, even with larger companies, it’s rare for everyone to be on the phone at the same time, so you can get away with a higher phone to SIP channel ratio.

Smaller Companies Need a Lower Ratio

If your company has fewer than 50 employees, the 3:1 phone to SIP trunk ratio, might not help you determine how many SIP trunks you need. This is because the smaller the office, the higher the chance that everyone is going to be on the phone. 

Small-to-Medium Businesses

If you own a small to medium-size business (SMB), you are probably looking for a flexible phone system that allows you to grow your business. At the same time, you’re also likely to be focused on your budget, and your company’s growth may be unpredictable. Your company could grow overnight, or you could stay the same size for years. That’s why it is important to find a SIP trunk provider that will let you order or cancel SIP channels on demand.

A lot of SMBs will use virtual work set-ups allowing remote employees to work out of the office to save money. SIP trunks are ideal for this situation. SIP trunks also support SMBs remote workers better than PRIs because there’s no need for circuits and cabling, allowing employees to access your business’ communication from anywhere. 

What makes SIP trunking so appealing to SMBs, is the flexibility. Typically the Primary Rate Interface (PRI), for the standard 23 channel circuit, is usually more than the number of an SMB’s employees. With SIP trunks you can get, and pay for, only the exact number of channels that your business needs at any given time.

Mid-to-Large Businesses 

If you have a mid to large company, you are likely looking at your telecommunications solutions from a much wider lens. You might need hundreds or thousands of channels, especially if have enterprise locations across the world. 

Your employees are likely going, coming, and moving to new locations frequently, so you’ll need a telecommunication system that can move as fast as your company does. This means you will need to be able to add new features and locations quickly. 

Your budget might not be as big of a concern as it would be for an SMB, but of course, you’re still considering your budget, every business does. Anywhere you can save money is significant. 

If you use SIP trunking, then your capital expenses can be reduced, and your telecommunications are turned into an operating expense which helps with your enterprise forecasting and budgeting. Also, keep in mind, SIP trunking will bring down the total cost of ownership for your hardware, which is always important. 

Your customers want reliability, and you want to make sure you can meet up to their expectations without any delays in customer service. The right number of SIP channels deliver high continuity and reliability in your communication.

SIP trunking is able to automatically reroute your calls to another location even if your call system is taken offline. This makes your customer service effective and efficient.

SIP trunking allows your medium to large business to save money and be flexible. Because SIP trunks are relatively inexpensive you can focus on your company’s needs and concerns, and let that dictate what the right SIP package is for your company. 

Determine How Many SIP Trunk Channels Your Company Needs 

Now that you see there are various factors that affect you SIP trunk calculations, it’s time to figure out how many SIP channels you need. This number is reliant on the size of your company, call volume, and nature of your business. There are ratios and calculations that can help you determine this number, but if you are still unsure, contact us, we are happy to help.

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