How Many Megabytes for One Minute of Conversation?

VoIP data usage refers to the number of kilobytes and megabytes used in a cellular data plan, but most data usage calculators do not include VoIP data in data plan estimates. Furthermore, a variety of factors influence the rate of data consumption, but a safe estimate is 0.75 MB per minute of conversation.

If you'd like to know precisely how much VoIP data you use, here is a way to estimate the bandwidth and minutes needed for your phone calls.

Calculate Minutes Per Month

First, estimate the amount of calling minutes you will need per month, including both outgoing and incoming calls. One way to do this is to pick a month and look through your phone's call history, counting the total number of minutes you were on a call. For the best estimate, consult multiple months and average the totals. Alternatively, plan a sample month and note the duration of calls you make and receive over the course of that month.

You will want to differentiate between the types of calls you make. There are calls that need to go through GSM. You will choose VoIP for international calls, calls with contacts using the same VoIP service, and calls that are free locally through a particular VoIP service, such as Gmail Calling.

Calculate Data Per Minute

To know exactly how many bytes a voice conversation consumes, you need to know which codec your VoIP service uses. A codec is a compression engine that transforms your (analog) voice into digital data, removing the silent moments (which make up to half of all conversations), and other processes that lessen the data load.

Here are approximate data consumption values for the most common VoIP codecs:

• G.711 - 87Kbps
• G.729 - 32 Kbps
• G.723.1 - 22 Kbps
• G.723.1 - 21 Kbps
• G.726 – 55 Kbps
• G.726 – 47 Kbps
• G.728 - 32 Kbps

These values will help you calculate data rates. For example, for one minute of talk with the G.729 codec, do the following calculation:

G.729 takes 32 kilobits per second,

which is 1920 kilobits (60 x 32) in one minute,

which in turn is 240 kilobytes (KB) per minute (1 byte is 8 bits)

Now that’s only for the data going out. Inbound data (which also counts) consumes the same amount of data, so double the figure to get 480 KB.

Finally, round the value up to 0.5 MB per minute of conversation.

Final Considerations

Other parameters may affect these values. Among them are the size (payload) of the voice packets, the intervals at which they are sent, and the number of packets sent per second (frequency).

Most people, however, only need an approximation of monthly data usage, so you don't need to be super precise. Also, you may not know which codec is being used. To that end, it's safe to assume an average value of 50 kbps for any codec. This gives an estimate of roughly 0.75 MB per minute of conversation. So, if you have an hour-long conversation, it will consume roughly 45 MB of data.