Beginner's guide: choosing a data package for your mobile broadband dongle

One of the most common questions we're asked on the forum (along with “can I use mobile broadband abroad?”) is about how much data is needed for mobile broadband. Unless you're familiar with such things, being asked how many gigabytes you require when shopping for a dongle is almost certainly going to result in confusion, and I suspect there are lots of people out there with unsuitable packages as a result.

All mobile broadband deals have a set data allowance, measured in gigabytes. When you run out you may be - depending on the package - charged automatically or required to purchase more credit in order to continue browsing ( T-mobile has a fair usage policy so you won't be automatically charged for exceeding the limit, but may have the connection restricted if you regularly run over or use a very large amount).

When purchasing a contract mobile broadband deal you need to think about how much data you'll be using to avoid unnecessary extra costs. The problem is, how are you supposed to know?

What affects the data allowance?

Everything you do online will use data, and that includes uploading files as well as downloading. Visiting a web site, watching a video, storing photos on Flickr – it will all use your data allowance.

You need to consider your typical behaviour and try to work out roughly how much you might need. There isn't any really accurate way of doing this and you'll find all sorts of estimates for how much data different activities use, but here's a rough guide to the data usage of various online pastimes:

1 hour instant messaging: 0.25-1Mb
1 hour web browsing: 1.5-25Mb
Streaming 1 hour of video: 250-500Mb
Streaming 1 hour of audio: 50-150Mb

Note that when networks say things like “1GB will give you 50 hours web browsing, 5 hours video, 7 hours music” in the marketing blurb they probably mean it will let you do one of those things, not all of it together (take a look at our MBB data usage guide here for more about the guidelines provided by networks).

You'll notice the spread in our figures is quite varied and the reason, aside from them being rough estimates, is that every site is different. If you go to Google.com it's not using much data at all as it's just a search box, graphic and small amount of text. But head to a site with lots of pictures and multimedia content like BBC News or Flash game emporium Newgrounds and your usage will shoot up. 25Mb would be an extremely busy page, but a few Mb per site is not unusual.

1Gb is 1000Mb. If we take 2Mb as a typical size for a site that gives you 500 visits. In reality you should be able to view many more than that as not only does a normal web browser store graphics and other data in its 'cache' on your hard drive to avoid having to download it again each time (so multiple visits to the same site won't use the same amount of data), but many pages will be smaller than 2Mb. If most of what you do is web browsing then 1-3Gb will allow you to view many, many web sites.

It's also important to note that some dongles will automatically compress images to reduce the size of pages. This means pages load quicker and you'll get more web for your Mb, but picture quality is reduced.

The big killers are audio and video. Streaming from YouTube, 4od, iPlayer and the rest is where data allowances really start to take a hit. Playing web games like Facebook's popular Farmville will also have an impact. If this is something you do on a regular basis then you'll want to start looking at the larger packages like those offering 7-15Gb. Ideally though these things are best done on a home broadband connection, which is almost certainly going to be faster as well as less restrictive.

Downloads and email

Email will vary depending on how you access your messages. Downloading your mail to the computer through Outlook uses a lot more data as you're grabbing the complete message plus any attachments, but viewing a web mail account is just like browsing a web site, and you only save the attachments you really want. For this reason we'd recommend always using a web mail service with mobile broadband

Downloads are easy to work out – just look at the file size and you can see how much you'll get for your monthly allowance. Anyone who regularly downloads big files will need a package with a large allowance, but lots of small files can easily consume same amount of data so be careful if you regularly use services like iTunes to get music.

One thing to watch out for is that your computer isn't downloading data in the background without your knowledge. Many programs are setup to automatically update and this will quietly eat away at your allowance. Anti-virus and other security applications can usually be left alone, not only for safety but because the updates are probably quite small.

More of a concern are Microsoft Windows auto-updates which can be hefty. Another common culprit is Adobe software such as Acrobat Reader which likes to quietly download updates without letting anyone know. Check the settings on all your non-essential programs to disable auto-updates when using a dongle.

Measuring usage

The numbers quoted above for data usage are only a guide so if you want a more accurate estimate you'll need to measure it yourself. There are lots of programs out there to do this, some free and some paid for. One of the best is DUMeter which isn't free but can be used for 30 days without handing over any money. Using DUMeter you can monitor how much data is used visiting favourite sites or carrying out typical tasks like uploading photos, and extrapolate that over a month to get a much better idea of your data needs (adding a bit extra for safety, of course).

When it comes to monitoring your mobile broadband usage to ensure you don't exceed the limit, we wouldn't recommend any third party program. If you wanted to dispute extra charges the networks are probably not going to care that your monitor app says you were within the allowance as they will only go by the information on their system. Instead, you need to find out from your network their approved method, which may be a feature built in to the dongle software or an online tool.

If this is a major concern for you then double check it with the network before buying a dongle, and make sure you are aware of the penalties for exceeding the allowance. Just try not to get to obsessed with watching those numbers, unless you go completely internet crazy or have a very low allowance you shouldn't encounter any problems.