Is per MB billing stealing your data?

12 September 2013

Providers don’t just measure exactly how much data you’ve gone through and detract that from your cap; it’s not that simple. Instead, things are measured in “sessions”. How long a session is can vary from a new one being generated every time you use an internet service, to a single session that can last close to a whole day.

Each session is then rounded up to either the next closest kilobyte (KB) or megabyte (MB). This is where a lot of your data may suddenly disappear. Depending on your carrier, you may actually be missing out on quite a bit of what you thought was your monthly data cap.


If your provider measures in KBs then logging on to check an email or Facebook is likely not going to go through much data. Emails especially can be as small as 10KB. As such, no matter how long your session is, your provider will charge you for the exact number KB you used, rounding up to the nearest whole KB.


A megabyte is 1024 kilobytes. If your provider measures in MB your minimum charge will be for a full MB, even if you only check a 10KB email. That means you are being taxed 1024KB, but only actually getting to use 10 of them. Every time you start a new session you will be using a minimum of 1MB. Thanks to the wealth of internet services on modern smartphones this can rack up incredibly quickly, especially for those with low data caps.

How can you tell?

A good way to tell is to look at your monthly bill. If the data charges on it never fall below 1MB then there’s a good chance you’re being measured per MB. You should also be able to log on as a customer and check the details of your specific plan. This will usually be found via a link labelled “Critical Information Summary.” These CIS documents have a lot of small print, so hit ctrl+f and do a search for terms like “data” or “per” and go through the results one by one.

Excess fees

Just because your included data is calculated in KB does not mean that your excess data fees will also. In fact, many providers that calculate in KB switch to MB once you’re over your cap. This makes using excess data even more dangerous, as you can be charged for a full MB at excess rates even if you only use a few KB in a single session.

How the big four calculate included data

Telstra, Optus, Virgin Mobile and Vodafone all tend to use per KB calculations, although not always. If you’re on an older plan, or recharge using prepaid, you might find yourself getting charged in multiple KB or MB increments.

  • Prepaid – per 1KB
  • Postpaid Red plans – per 1KB
  • Prepaid – per 1MB
  • Postpaid Every Day Connect Plans – per 1KB
  • Postpaid Data Packs – per 1KB

*Telstra’s CIS for its Every Day Connect and Freedom Connect plans state that it is billed monthly. However, a rep on Telstra’s own site has stated that this is incorrect and that Telstra data is calculated per 1KB.

Virgin Mobile:

How MVNOs calculate included data

Mobile Virtual Network Operators (MVNOs) essentially rent space on a larger network (Telstra, Optus, Vodafone) and resell that capacity to their customers. Technically Virgin Mobile is an MVNO, as it operates on the Optus network, but it's a large enough provider to be considered one of Australia's major players. Some of the more well-known MVNOs currently operating are ALDImobile, amaysim, Boost Mobile and TPG, among many others.

MVNOs generally lean towards either calculating included data per KB, or offering on unlimited plans that require no such calculations. However, some MVNOs do calculate per MB.

We can't cover every Australian MVNO here, so if yours isn't on the list try looking up your plan and searching for the Critical Information Summary.

Bendigo Bank:
  • Postpaid – per 1 KB
  • Monthly – per 1KB

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