More and more companies are moving to modern business phone systems that reduce costs and help their offices run better. But how do you know if you’ve got the right Internet speed to make the move? Getting your business VoIP-ready comes down to what’s called functional bandwidth.

Calculating bandwidth doesn't require busting out the graphing calculator, just a little basic multiplication.
Calculating bandwidth for a virtual phone system doesn't have to be a head-scratcher

Functional bandwidth simply means how the speed you're buying from your Internet service provider (ISP) translates to your day-to-day office work. Don’t be skerred if you don’t have an IT pro handy. It’s actually pretty easy math once you know how to do it!!!

Knowing your functional bandwidth will make sure your current connection offers enough oomph to keep your data flowing and ensure good call quality when you connect your new business phones and unified communications software. 

First, a little prep work. Gather these two things:

  1. Your normal upload and bandwidth speeds. Find this on your Internet bill, or run a Speed Test.
  2. The number of business phones in your office, including those in conference rooms.

Here’s a basic formula to decide whether your network may need a bit more bandwidth before you make the switch to a virtual phone system…

Dust off your 3rd grade math

Think of your office's bandwidth as a two-way street, taking in and spitting out data. This means you need to think about both the upload and the download speed of your Internet access. Using the number of phones you gathered above, let's run the numbers:

# of Business Phones 
X .09 megabits per second (Mbps) 
= Recommended minimum bandwidth

Next-level stuff

This quick calculation covers the minimum bandwidth we recommend. Your business should consider boosting your speeds above this if you do a lot of data-dependent tasks such as: 

Streaming and sharing screens. Folks who do a lot of training via video conferencing or screen sharing to help customers will want more than the bare minimum. High-quality, multi-location video conferences can require up to 1.5 Mbps each. Don't get us started on YouTube and Pandora.

Contact center call volumes. Ask about more bandwidth to handle increased concurrent calls when your office acts like a call center taking a lot of sales inquiries, customer service or technical support.

Other Internet-based services. If you have cloud-enabled security cameras, backup service, or business software (i.e. accounting packages, document storage, design suites), make sure you've got extra wiggle room.

Beyond bandwidth, there's some more technical stuff you may also want to consier. For example, packet loss and latency can affect call quality. Check your connection at We also suggest working with your prospective VoIP business phone system provider to ensure your router will have Quality of Service (QoS) to protect call quality. 


Multiplying by two approximates the regular Internet traffic from a similar number of computers. This calculation provides a minimum download and upload speed to make sure the voice calls and data your cloud phone system with VoIP phones will play well with your other Internet use.

Upload speeds are often lower than download, so for most people that's the one to watch when comparing the results of this little equation with your current bandwidth.

A good rule of thumb

If you don’t want to do the math or aren’t sure how much to add for the added data needs in the sidebar, here's a good rule of thumb. With bandwidth prices dropping and the savings you’re likely to experience versus keeping traditional business phone lines, go with the old adage “the more the merrier.”

We find a typical office works best with download speeds from 10 and 50 megabits per second (Mbps) and upload speeds of at least 3 to 10 Mbps. 

Taking the next steps

If you’re checking bandwidth, you’re probably already considering make a move from traditional phone lines like a PBX system or just regular landlines to VoIP – or from one business VoIP provider to another. Here are three steps we suggest to make a sound decision:

  1. Compare apples to apples. What do you have now, and what does it cost? How do those benefits and costs compare to what your new potential business VoIP providers offer? We think you can get more features and potentially save your business a bundle. We recently heard from a restaurant chain that one of its franchisees is saving $300 per month yet getting way more than just a dial tone!
  2. Take a test drive. Look for a free, no-commitment live demo where you can ask questions.
  3. Seek expert help. We offer a free Buyers Guide to help you make a good decision for your business.