Is it possible to know how long time one whole site takes by 250, 500 or 750kbps or 1, 2 or 4MB?

Question

I'm a web designer and will make a document to train my sites clients how to know if the internet bandwidth speed is slow or quick for each visitor of their sites, depending on the images or site weight (in bytes or in megabytes) and on their internet speed (in kilobit or megabit), for taking how long seconds or time by 250, 500 or 750kb and 1, 2, 4 or 10MB.

Answer 1

I guess there are a few different ways to look at that question. If you are just looking to calculate how quickly the data can be downloaded in a perfect world, Jim's answer explains doing that calculation. But simply downloading files is a small part of the overall performance of a site. There are a few tools out there which will help you understand the performance of your site at different connection speeds.

One of those tools is Webpagetest.org. Enter your URL, choose a location and a browser then expand the Advanced Settings section. Choose a connection type and enter the number of times to run the test. It should be more than 1, but you are limited to only 10 through this UI. Its probably a good idea to go over to the Video tab and choose to capture a video as well so that you can demonstrate what its like on each size pipe. Then repeat for each of the connection types you want to test. This will give you a pretty good idea of how long it will take to view this site at different connection types.

The downside here is that its a bit of work to create a bunch of tests, then collate that info. An alternative to this is the Site Monitor feature at http://yottaa.com. You can setup a single test which will look at the site from different locations, or different browsers, or different connection types, then let you easily graph out the results. To get access you have to register for a free account. An alternative to that is at http://websitetest.com which requires no registration, but you get none of the management of test results.

Webpagetest.org is run by Google in cooperation with a lot of other partners.

Full Disclosure: I am the Technical Evangelist at Yottaa.

Answer 2

If you're asking how long it takes to download, say, 54 megabytes on a 10 megabit (or whatever) connection, the simple solution is pretty easy.

For the sake of simplicity, and to take into account the overhead involved in TCP communications, we typically say that 10 megabits per second is the same as one megabyte per second (that is, we assume one byte is 10 bits rather than 8 bits).

So if you want to know how long it takes to download 54 megabytes on a 10 megabit (1 megabyte per second) connection, the answer is 54/1, or 54 seconds. If you have a 250 Kb connection, that's 25 kilobytes per second, or 0.025 megabytes per second. 54/0.025 = 2,160 seconds, or 36 minutes.

In general, this is a best case estimate. It assumes that the connection between client and server can support the sustained maximum rate. The numbers don't take into account other things the server might be doing that would reduce the bandwidth it can dedicate to a particular connection, nor does it include stalls that could occur in the many hops between client and server.

In practice, the number will most likely be larger. That is, if the above calculation says that the entire site can be downloaded in 27 seconds, it could easily take twice that long. There's no way to reliably predict, based only on the client's bandwidth.

It's also possible that it could take less time, if the client's "10 megabits" is an average, and bursts of higher bandwidth are available. Especially during times of lower overall network usage.