What is the best way to calculate bandwidth needed for my website?

Question

What is the best way to accurately calculate bandwidth needed for my site?

I have come across several formulas and wondering what one is the most accurate?

Here are a couple examples:

(Average Daily Visitors x Average Page Views x Average Page Size) + 
(Average Daily File Downloads x Average File Size) x 31 x Fudge Factor

Source

and

amount of visitors * the size of one page = total bandwidth needed 

Source

So what is the best way?

Thanks!

Answer 1

There are many factors that can, and should, make these formulas deprecated, and give values that goes too far away from the real value:

• If you have a lot of images that do not origin from your web server;
• If you cache a lot of things on the client-side with .htaccess or others ways;
• The way your website is build, with a lot of AJAX just loading some bytes of data to go to a new page;

But you should go for the first formula, remembering that the average page views it's not the total page views of the website but the average number of pages that each visitor visits!