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Internet service providers offer a wide range of broadband plans to suit the needs of the majority of potential users. These plans quote the quantity of included data – downloads and uploads – in gigabytes (GB), or even terabytes (TB) in some cases. To give a sense of scale, a CD can hold about 700 megabytes of data, while a DVD can hold about 4.7 gigabytes.
A ‘byte’ comprises eight ‘bits’ – enough to represent a letter from the English alphabet. These are the ‘bits’ we are talking about when we say we have a data speed of, say, 12 megabits per second (Mbps). The size of files, usually expressed in kilobytes, is displayed in file folders on your PC and alongside files that you are being invited to download.
Table 1 explains data volume terminology and gives some easily recognisable examples of how this translates to everyday usage. Using this knowledge you will be able to monitor the size of files that you’re downloading and uploading, and get a feeling for how many gigabytes you need to send or receive in a month. The amount of data you expect to use will determine your choice of data plan.
Table 1: Data volume terminology
| Bit | Byte | Kilobyte | Megabyte | Gigabyte | Terabyte |
| 1 Bit | 8 Bits | 1000 bytes | 1000 kilobytes | 1000 megabytes | 1000 gigabytes |
| What can you do with these bytes | |||||
| Add another 7 bits and get a byte | Not much – this is only one English language character | Send or receive seven tweets on Twitter | Send or receive 40 emails (25 words each) without attachments | Download a standard definition movie (about 100 minutes long) | 1000 gigabytes |
Mobile data: what you need to know: Wikipedia 
Plans will range between 10 and 1000 gigabytes per month, and prices will range from $30 to $300 per month. Many of these plans involve what are known as 'bundles' that include fixed telephone line rental and calls, and possibly also pay TV services.
Enter searches such as ‘what size data plan do i need’ into a search engine (e.g. Google, bing or Yahoo!) and you will discover helpful sites such as WhistleOut’s guide to calculating your data needs, Vodafone's mobile broadband data calculator and Telstra’s data usage calculator.
Pay attention to expressions like 'data cap' or 'capped data' in plan descriptions. You need to know if you will be charged more – often a lot more – if you exceed the monthly limit (i.e. the data 'cap'). Alternatively, some providers may restrict your download speed (referred to as 'throttled' or 'shaped') when the cap is reached.
