Friday, January 19, 2018
Mobile Data – Explained

Mobile Data – Explained


When buying a new phone or contract you have undoubtedly heard about Mobile Data. Mobile Data refers to the data you use when you are connected to a 3G network (for the difference between 3G and WiFi see our article, What is the difference between 3G and WiFi?). This article will explain what mobile data is and explain how it is used.


Whenever you are using the internet on your phone you are using data. Data is measured in Megabytes (MB) and Gigabytes (GB). A gigabyte is about 1000 megabytes (more specifically it is 1024 MB) so a good way to remember the difference is to liken megabytes to grams and gigabytes to kilograms.

You don’t just use data on your phone when you are on your browser, but every time you use an app connected to the internet like Facebook, Twitter, Google Maps, Email, Whatsapp etc.

To illustrate how using the internet uses data let us use an analogy.

The Courier

When you do something on the internet you are basically sending a request to a website and they send you back the data you want.  For example, when you search something on Google you are sending a request to Google saying “show me what you know about cats”, for example, and they send you back a list of links to pages on cats. To understand mobile data, we can reimagine this as you sending a letter to Google:

Dear Google,

Please can you tell me where on the internet I can find more information on cats.

Yours sincerely,

Internet User

And they respond with a letter saying:

Dear Internet User,

Here are all the links we think are relevent to you:

Yours sincerely,


To get these letters to and from Google you have hired a courier. You pay this courier based on the weight of letter or parcel he takes from you to Google or from Google to you.

Letters like the one above containing text only are very light so they won’t cost you a lot.

You now send a letter to Google requesting images of cats. The letter they send back is much heavier because it contains 20 photos of cats each printed on lovely heavy glossy photo card. So letters containing images will weigh more and cost more for your courier to transport.

Similarly if you requested a song about cats or a film on cats from Google the parcel would be much heavier. Imagine the courier bringing back a CD or an old style film reel. These sorts of things weigh a lot so cost a lot for the courier to take back and forth.

The courier in this scenario is much like the company providing your access to the internet. Instead of charging by weight, they charge by the amount of data that has to be transferred over their network. Things like text only emails or websites are not very “heavy” – they contain little data – whereas things like music or films are much “heavier” – they contain a lot of data.

Much like you pay the courier by weight, you pay the internet provider by the amount of data they have to “carry” across their network.


If we continue the courier analogy there are two ways you can pay for the couriers service.

  1. Per trip
  2. Per month

Per Trip AKA Pay-As-You-Go

Let’s say you pay the courier 1p per gram for the amount he has to carry on his trip. So if you give him a letter weighing 5 grams, and Google give him a letter weighing 5 grams then you have had to pay 10p for that round trip.

This is the same as if you have a “pay-as-you-go” (PAYG) package for mobile data. You pay for every bit of data you send or receive, but no more.

Per Month AKA Pay Monthly

If you are sending and receiving enough mail with the courier you may decide it’s easier to pay him per month for a certain amount of weight. This arrangement is better for the courier as well so the courier may agree to carry 500g a month for you for slightly less than it would cost per trip. Lets say £3 instead of £5. The downside of this arrangement for you is that you have to pay him whether you send and receive 500g worth of stuff or not. Furthermore, if you go over this limit you still have to pay per trip like you would normally.

This is the same as pay monthly contracts. It is very common to get a data allowance (a certain amount of data you can use each month) bundled with minutes and texts in a contract. Data allowances are typically around 500MB – 1GB.

If you feel you will use a lot of data in a month and will regularly use more than the data in an allowance you can pay to be able to transfer as much data as you like per month for a flat fee. This usually costs quite a bit more than having a data allowance, but you have the freedom to use as much data as you like. This would be the equivalent of hiring the courier for, lets say, £40 a month to carry as much mail as you like.

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