How Much Bandwidth Do I Need for VoIP?

concurrent users play a role in determining voip bandwidth

What Are The Speed Requirements For Hosted VoIP?

how much bandwidth connection speed need voip
Along with “What is VoIP?“, we hear this question all the time, “do I have enough bandwidth for VoIP?”, when someone is considering switching to a VoIP phone system.  Technically, “bandwidth” is more related to what is being transmitted over the internet rather than how fast an internet connection is. However, asking “how much bandwidth do I need for VoIP?” can be used interchangeably with “what is the speed requirement for VoIP?”.

Bandwidth is measured in units called a “Hertz”.  A Hertz is used to identify the range of all the different frequencies travelling through the air from broadcast television, radio, cell phones, etc.

The internet connection speed, also called the “bit rate”, is measured in “bits per second”.  The numbers used indicate how much data can be sent (upload) or received (download).  Your internet provider controls the “flow” of how much data can be sent/received based on the plan you purchased.  If necessary for a VoIP phone system, a simple phone call to your internet service provider may be all it takes to increase the connection speed,

Cable companies offer internet plans that start around one or two mega-bits per second and they go up from there.  Remember that the plan speed is a maximum value and you may experience connection speeds “up to” the plan limit.  An internet speed test site may give you a more realistic measurement.

Connection speeds are almost always indicated with the acronym Kbps (Kilo (one thousand) bits per second) or Mbps (Mega (one million) bits per second).  These should not be confused with “bytes”, which is used to measure data storage capacity.

Your connection speed affects everything you do over the internet.  The time it takes to transfer anything (voice, search results, videos, financial reports, stock updates, etc.) all depends on your connection speed.  The greater the connection speed the better overall experience.

upload and download speeds are not the sameAre the upload and download speeds the same from my internet service provider (ISP)?

No, generally they are not.  The upload speed is typically much slower than the download speed.  The upload speed is the figure you should use when determining hosted VoIP speed requirements.

The general rule that we use at VOIP O.C. is 100 Kbps per phone line. While voice compression can be adjusted to increase the Quality of Service (QoS) when lower connection speeds are all that is available, we use a standard compression (G.711 uLaw) to provide the best call quality.

Compression squeezes the sound into a small packet before sending it over the internet. Too much compression and the sound quality really begins to suffer.  Not enough compression and your phone calls can impede other traffic over your internet connection.

To help us calculate how much bandwidth is needed for a VoIP phone system, as an example, an office with six phone lines may consider the following results:

Speed per phone line 100Kbps
Number of phone lines 6
Maximum voice data 600Kbps

While this scenario could get by with an upload internet connection speed of 1Mbps, we would prefer to see 2Mbps.  Why the extra connection speed?  Remember, this is only the voice data being transmitted over the internet connection.  There are many other factors to consider.

Here are some things to keep in mind when estimating the total connection speed needed for a VoIP phone system in your office:

  • What percent of the time will all users be on the phone at the same time?
  • What are the peak phone traffic times of the day?
  • What other software or activities will utilize the internet connection?

What if we don’t use the phone all the time?concurrent users play a role in determining voip bandwidth

You can play with these estimates by considering the first point above. If you have office staff who are on the phone constantly, they will use nearly all of the estimated speed for their phone line.  If you have other staff who use the phone 25% of their day, then the four of them combined will use the estimated speed for one phone line.  What we’re planning for is the scenario where all phone lines are in use at the same time. Again, it is better to have more than not enough.  Here is a general rule of thumb that we use to calculate concurrent usage, which has proven to be fairly reliable in our 10 years in the industry:

Office with standard phone usage One call for every four extensions
Office with above average phone usage One call for every three extensions
Office with heavy phone usage One call for every two extensions

We would appreciate the opportunity to answer any questions you may have regarding this topic or anything phone related.  Feel free to contact us any time.