Formula for Disk Space Usage

Disk space is fairly easy to calculate.
Bandwidth is more difficult to calculate as it depends on a variety of factors.

Disk Space:
How much space do the contents take up on your computer's hard drive? They should take up (basically) the same amount of space on your server. If you have 1,067,512 bytes of site data residing on your hard drive before you upload it to your site, it should take pretty much the same amount of space on your server (just over 1 megabyte).
Add to this any overhead created by any content management system(s), scripts, etc that reside on your site but not on your local hard drive. Most scripts and content managers and the likes will give at least an approximate measurement of this. (and if you're installing through an interface like Fantasico, then you'll see the space requirement before installing).

After this, if your site utilizes a database, then your disk space needs get a little fuzzier as the disk space will grow as the database becomes more populated. Though you can roughly calculate the space requirement for the database once you know how large the contents for one complete record would be. Then multiply this times the number of records you estimate the database will contain.

This isn't an absolute calculation, but it should provide you with a guideline as to how much space you need.

Bandwidth is complicated by what kind of content you are providing at the site, how it is delivered, how popular the site becomes and what percentage of the site your users will be downloading as well as how often.

If you are offering a 300 kilobyte web page (several decent web graphics and several pages worth of text), then every 3 page loads would equal about 1 megabyte of bandwidth.

If you are selling a digital product using an expiring download link, then most paying customers should only need to download the product 1 time (allowing bandwidth for say 5 downloads for every 4 customers allows some leeway for those customers who are disconnected and have to restart their downloads)

If the digital product is 2.5 megabytes in size, and assuming 5 downloads per 4 customers, you would need to allow 12.5 megabytes of bandwidth for every 4 customers, in addition to your other pages (sales pages, squeeze pages, etc)

Since I use a reseller hosting account, I have several plans set up, one is a basic "while I'm building it" package that includes limited hard drive space, and limited bandwidth, since I'm pretty much the only one using the site.

When I launch the site, I usually assume that the site needs enough bandwidth for the entire site to be downloaded at least 5 times in the month, if it is a large site that no one will be downloading all of. If it's a small site, I start with 50-80 complete site downloads worth of bandwidth.

Then I keep an eye on it as promotion gets going. It's easy with the right reseller account to step a site's limits up in a couple of minutes, but this also allows me to kill a site fast if for some reason something is hideously wrong.

But generally speaking if the site's contents are under 10 megabytes, I usually start at about 500 megabytes of bandwidth allowance for the month. If the site is significantly larger (or if I have any reason to expect it to take off quickly), then I will set the bandwidth allowance higher.

I hope this helps, I know it's not a real straightforward formula, but it is what I use for my new sites.

Wow Scott,

Thank you so very much, this is very helpful to me. Trying to decide if I should go with a reseller account.

Thanks,

Z