KB109 - Calculating VoIP Bandwidth

One of the key drivers for new VoIP deployments is the lower cost when compared to traditional telephony solutions, and a major reason for the lower costs is the type of connectivity required to connect a customer’s phone system to the rest of the global telephone network. Whereas traditional phone systems require dedicated, always-available circuits to terminate voice calls, VoIP systems are able to allocate the bandwidth they require on demand; when there is no active call, the bandwidth is free for use by other applications, resulting in more efficient resource utilization.

One result of this new model is the fact that bandwidth capacity planning is an important part of any new VoIP deployment. Fortunately, Clearfly utilizes fixed-bandwidth voice codecs and a fixed packetization interval of 20 milliseconds, which means that once all of the variables are taken into consideration the calculations themselves are quite straightforward.

WAN Type:

Per 20ms Interval

Per Call


Signaling overhead is commonly estimated at 5% of the media bandwidth.

Packet Layout