A popular misconception among many people, as well as web hosting providers, is that bandwidth and data transfer are the same. This is probably due to the fact that they are very closely linked, but for anyone who is subscribed to a web hosting service, knowing the difference can save both time and money.

Put simply, bandwidth is the quantity of data that can be transferred from a website at any one time, while data transfer is the amount transferred over a period of time. This is where the water and pipes come in. A pipe would be bandwidth – the bigger the pipe, the more water could pass through. However, data transfer would be the amount of water in the pipe in a month, for example. Essentially, data transfer is the use of bandwidth.
Why should you care?

The lower your bandwidth provided by your web hosting provider, the slower your site will download to users’ computers, irrespective of how fast their Internet connections are. If multiple users are accessing your site at once, they may find that they experience extremely slow, or no, connectivity.

Data transfer allowances control how much data can be transferred from your site over a certain time. For example, a web hosting provider may impose a limit of 2 gigabytes of data per month. If your website exceeds this, it may be taken offline until the next month.
You will often be given an option to upgrade your bandwidth or data transfer allowance, and even the more affordable web site hosting plans can give you flexibility in this department.

So what do you need?

Unfortunately, the confusion between bandwidth and data transfer is now widespread, and the two terms have become interchangeable.

Normally, web hosts will refer to data transfer as bandwidth. If you’ve already got a site online, it’s very easy to estimate how much data transfer allowance you’ll need. Statistics such as number of visitors per day enable you to calculate roughly how much will be downloaded from your site per month.

If you haven’t got the site up and running, you should estimate using quite an optimistic guess, particularly if you plan on investing in advertising campaigns.

In either case, use the equation below to get an estimated monthly data transfer figure:
Number of expected visitor x Average size of pages (including graphics) x Expected number of pages viewed per visit x 30 = Monthly Data Transfer

Bandwidth is rarely under your control

Bandwidth, unlike data transfer, cannot normally be increased. It is an extremely expensive commodity. The more visitors looking at a website, the less bandwidth there is available, and the slower the site will download. Getting a web hosting solution with good bandwidth is really important.

Throttling, the limiting of the number of users able to view your website at the same time, is sometimes a method employed by web hosting companies (particularly on the more affordable web site hosting plans) to keep websites within their bandwidth restrictions. If you think this may negatively affect your website, get in contact with the web hosting company for more information.

What you can do

A large part of all computer-based work is to do with efficiency, and this is especially true of web design, particularly when working within the confines of a web site hosting plan. By making simpler, efficient websites, you can reduce both the amount of bandwidth and data transfer your site uses.

Simple things like using more space-efficient graphic formats (such as highly compressed JPEGs), separating JavaScript into a separate file from the HTML, using CSS (Cascading Style Sheets) and trimming down unnecessary white space in HTML files can all help reduce the amount of data flowing out of your site, and allow you to stick with affordable web hosting plan.

Allowing your website to be cached by web browsers is also a great way to keep data transfer down, although using an “Expires” META tag might be a good idea so that users don’t end up accidentally seeing old versions of your site.