To estimate your bandwidth usage multiply the size of your average page, including the size of images included in the page, by the number of times that page will be viewed in a given month. Multiply that number by the number of pages in your website. This will give you an overestimate of actual use.
If the average page on your site was 20,000 bytes (20K), and was viewed 500 times and you had 50 pages, your bandwidth usage for the month would be around 500,000,000 bytes or 0.5 G. This is only a rough estimate.
Your actual measurements can be determined by looking at your website stats at the end of each month.
Our hosting plans offer generous traffic allowances and, by the time you ever exceed them, you will have a very successful website that will be able to support any associated extra charges for bandwidth use.