Internet Download Time

Bits, Bytes
& Internet Speeds

Wednesday, June 28, 2017


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Bits, Bytes and Internet Speeds:

Binary Bits

A Little History

All computers use digital processors that communicate using binary bits. The name 'bit' is an abbreviation of b(inary dig)it.

In decimal, each digit can take the values 0 through 9, however a bit is a basic binary value that can only have the value of one or zero. The state of a bit is commonly referred to as being a 1 (ON) or a 0 (OFF).

Computers generally use the Byte, which consists of 8 bits for storing data. Using the binary numeral system an 8 bit Byte can hold the values of 0 through 255.

Internet Speeds

Broadband Internet providers market their services in bits per second, not to be confused with Bytes per second. Remember there are eight bits in a Byte. For example a 3 Mbps DSL connection can download at 3 million bits per second or 375 thousand Bytes per second.

Most home broadband services are also asymmetric, which simply means that more of the total bandwidth is dedicated to the download channel than to the upload. This is because most home users want to download far more data than they upload. For example you may have an ADSL plan that provides 3 Mbps download speed and 1 Mbps upload speed.

Internet Downloads

While Broadband services are measured in bits, computer files are not. They are measured in Bytes, Kilobytes, Megabytes, etc. To further confuse the issue a Megabyte has two different values depending on the context. For example computer hard drives are marketed using decimal values. A 500 MB drive can hold 500 million Bytes, however when you look at the size in Windows you will see 476.8 MB. This is due to the fact that the computer uses binary values such as 1024 for 1 Kilobyte, then 1024 Kilobytes for 1 Megabyte and 1024 Megabytes for 1 Gigabyte.

Estimate Your Download Time

Let's say you want to download an ISO image of a DVD containing Microsoft security updates and the file size is 3.4 GB.  http://www.microsoft.com/en-us/download/details.aspx?id=34953

How long will it take to download 3.4 Gigabytes using your 3 Mbps DSL connection?

First off, let me state that there is a lot of overhead involved when downloading files from the Internet. You have to factor in the speed and load of the server that you are attempting to download from. The file may be located on a server in another country. Your connection may have to be routed through multiple hops (different locations) to reach the download server. Many people may be trying to download the same file at the same time

A good rule of thumb is to allow at least 25% for overhead in the transfer.

Let's do the math!

You need to download a 3.4 GB file from the Internet.

1 Gigabyte = 1,073,741,824 Bytes

3.4 GB is approximately equal to 3,651,000,000 Bytes

A Byte is 8 Bits, so you need to download 29,208,000,000 Bits

Your 3 Mbps DSL connection can download 3,000,000 Bits per second.

If you divide 29,208,000,000 by 3,000,000 you get 9736 seconds.

9736 divided by 60 = 162 Minutes

Let's account for overhead. 162 times 1.25 (25%) = 203 Minutes

It will take approximately 3 Hours and 23 Minutes to complete your 3.4 GB download using a 3 Mbps DSL Internet connection.

Average File Sizes*

  • Document - 100 KB
  • Spreadsheet - 300 KB
  • JPEG Digital Photo - 2 MB
  • MP3 Music Song - 4 MB
  • MPEG Feature Length Film - 600 MB
  • CD Image - 750 MB
  • DVD5 Image - 4.7 GB
  • DVD9 (Dual Layer) Image - 8.5 GB
  • Blu-Ray Disk Image - 25 – 50 GB

*Note: These are average sizes. Exact file size will vary considerably depending on the specific content of your files.

Average Download Times (25% Overhead)

56 Kbps Dial-Up

  • 100 KB Doc File – 18 Seconds
  • 4 MB MP3 Song – 12.5 Minutes
  • 750 MB CD Image – 39 Hours

1.5 Mbps DSL*

  • 100 KB Doc File – 1 Second
  • 4 MB MP3 Song – 28 Seconds
  • 750 MB CD Image – 1.5 Hours
  • 4.7 GB DVD Image – 9.3 Hours

10 Mbps ADSL2+/Cable/Fiber*

  • 4 MB MP3 Song – 4 Seconds
  • 750 MB CD Image – 13 Minutes
  • 4.7 GB DVD Image – 1.4 Hours
  • 25 GB Blu-Ray Image – 7.5 Hours

50 Mbps Cable/Fiber*

  • 4 MB MP3 Song – 1 Second
  • 750 MB CD Image – 2.6 Minutes
  • 4.7 GB DVD Image – 16.8 Minutes
  • 25 GB Blu-Ray Image – 1.5 Hours

*Note: Broadband delivery technologies encompass a wide range of speeds.
You can determine your Internet speed here. http://speedtest.net


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Bits, Bytes and Internet Speeds

If you would like to comment on this content you can do so HERE.

  1. Robert Pearson says:

    Thanks for the fast response I tested by pluging laptop to cable then used speed test ping on speed test was 9ms

  2. admin says:

    What are you using to test the speed on the PS4 http://manuals.playstation.net/document/en/ps4/settings/nw_test.html

    A network connection always negotiates to the speed of the slowest device. Using cabled Ethernet, many routers, switches, game consoles are limited by the speed of the network ports, typically 100 Mbps (Fast Ethernet). To exceed 100 Mbps would require all devices and cables to be Gigabit (1000 Mbps).

    Remember that your Internet connection is shared, so all devices will share the limited bandwidth from the ISP. For gaming your speeds are more than adequate. You also need to know the latency (ping time) to the gaming server. Latency is the time in Milliseconds that it takes the signal to travel to the destination server and back. Shoot for something under 50 ms. Over 100 ms will cause lag.

    Good Luck…

  3. Robert Pearson says:

    excellent artical could I pick your brains on the subject of routers I have 126 down and 13 upload speed I play online games on a playstation 4 which is connected to my router with a cat 5e cable but my connection rarely feels great would a better router give me a better connection to other players rather than the router provided by my isp thank you

  4. Perry Mattes says:

    Dan, you are a master of logic, you’ve written a masterful article. Though you don’t say it, I assume there is great significance between a capital ‘B’ and a lower case ‘b’ as in MBps vs Mbps. Where can I read more of your stuff.

  5. admin says:

    Comments are welcome!


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