**Important** - this is only a rough concept
Often I am asked "how much bandwidth do I need?" To clear this up for some to roughly estimate bandwidth for a website I like to use the following calculation:
((Estimated Monthly Page Views X Average Page Size) + Downloads) x Safety Margin = Estimated Monthly Bandwidth
***VERY IMPORTANT NOTE*** all the units must be the same standard, I would suggest KB. At the end remember to change the units into something workable (so either GB or MB) a quick summary of conversion is as follows:
1MB = 1024KB
1GB = 1024MB
A brief explanation of each item in the calculation is a follows:
Estimated Monthly Page Views - How many pages are opened in a monthly period (total across the entire site).
Average Page Size - exactly as it says is the average page size of viewable pages.
Downloads - This is optional really and only applies if you have downloadable content so you estimate how many downloads and what size they will be on average.
Safety Margin - This is always >1, this is your safety margin so you don't exceed bandwidth. I would always suggest 1.2 (20%) to 1.5 (50%).