What is Bandwidth?

February 3, 2009 / Updated: February 3, 2009 / Lena Shore
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There are two kinds of bandwidth. I know. Confusing already. Bandwidth can refer to speed (how fast you can go) or it can refer to hosting (how much can you transfer).

Bandwidth (speed)

In the world of the internet, this is how fast you can go. How fast web pages show up when you click a link and how quickly downloads take to complete. This is mostly determined by your ISP (Internet Service Provider – Comcast, Bellsouth, etc.) and what plan you are on. Do you have a cable modem? DSL?  T1 line? Or are you still chugging along with dial-up?

Think of your bandwidth like a highway. The amount of lanes in the highway is bandwidth and how many cars are traveling on that highway is traffic. If you have four lanes of traffic at 4 a.m. you are probably one of the only people on the highway and can get to your destination quickly. If you want to go to the same destination at rush hour, you now how to share your lanes with a bunch of other cars and will be sitting for a while.

If you have a reputable ISP they may have 50 lanes of traffic for every 50 customers. If your ISP is Joe’s Discount Dial-up and Chicken Farm, he might only be providing one lane of traffic you have to share it with all of his other customers. So, you might not do so bad at 4 a.m. while you are the only one surfing – but at 5 p.m. when everyone else wants to surf the internet, you might be stuck behind a truck. A chicken truck.

Bandwidth (hosting)

If you have a web site and pay for hosting, you care about this kind of bandwidth. This is the amount of traffic your web site can handle before you start paying overage charges.


Each time a person comes to your web site they are accessing or downloading part of your web site on their computer. If you can see it on your computer screen, you’ve temporarily downloaded it. If you have a file for them to click to download, that also counts towards your bandwidth. Every time they view a new image or file, they are downloading. Each download will have a particular size.

The smallest unit of measurement we are going to talk about is a byte. Traffic is the number of bytes you are allowed to transfer. Most web sites are pretty small and bandwidth allowed is usually allocated in gigabytes (GB).

  • 1 byte = 8 bits
  • 1 kilobyte (KB) = 1024 bytes
  • 1 megabyte (MB) = 1024 kilobytes
  • 1 gigabyte (GB) = 1024 megabytes

Let’s pretend that a single jelly bean equals one byte of information for our next example:

  • Imagine that a candy factory has 1024 cases of jelly beans. 
  • Each case contains 1024 jars of jelly beans.
  • Each jar of jelly beans contains 1024 jelly beans.
  • If each jelly bean is one bit, the candy factory has 1 GIG of jelly beans.

File Sizes to Consider

  • A music file probably averages 4MB
  • A single page word document is about 28KB
  • Yahoo’s home page is about 70KB
  • CNN’s home page is about 200KB

Your website traffic

Let’s say your web site takes up 100MB of space. You have 20 web pages, a bunch of photos of your family, some video files, and a few documents for people to download. If I go to visit your site, I am only going to download the part I look at. If I only look at a couple of your web pages and one photo of your family, I will use less bandwidth than if I looked at all 20 pages, every photo, all the videos, and all the documents.

Example 1: Let’s say I look at a video that is 5MB in size. I have used 5MB of your bandwidth.Now, lets assume I tell 5 of my friends to also watch the same video. 5MB x 5 of my friends = 25MB of bandwidth. So, if my ISP allocates my bandwidth to 1 GIG, the video would have to be watched about 41 times to reach that limit. If someone watches it for the 42nd time, you will either get charged additional fees or your web service will be suspended until it resets – depending on your ISP.

Example 2: Let’s say that 100 people go to your home page, read it, and move on. If your home page was 100KB in size, that would be 10,000KB of bandwidth. Do that process 104 more times (10,400 people) to reach your bandwidth limit of 1 GIG.

This should give you an idea of how to calculate your own bandwidth and limitations. It’s also a good idea to add a fudge-factor since your bandwidth is never as straight forward as the examples above. Additionally, your host may have a way for you to track your own usage.

My hosting policy

And for those of you who host with me and are wondering what your own bandwidth limitations are? I don’t charge for extra bandwidth, so there’s nothing to be concerned with. I have enough things to be worried about already, and I figure you do too!