Mbit/s, Mbps, or MB/s

Filed in archive Performance on May 30, 2008

© casey.marshall

Do you get confused when talking data transfer rate. Do you want to compare disk drives, whether they be USB, Firewire, CD-ROM, SATA, or something else and can't relate them. Well we all know that high numbers of MB/s are better. But what about comparing devices when they are represented in different speed nominclature. Here I would like to help in this confusing endeavor. Bookmark it, share it, and save it for latter reference.

The best way I remember this whole confusing issue is by one simple little saying. Little 'b' equals little data (bits) and big 'B' equals big data (bytes). This may sound stupid but it is the only way I can delineate between bits and bytes. So how does this relate.

A megabit per second (Mbit/s or Mbps), most used is the Mbps, is equal to 1 million (1,000,000) bits per second.

To translate this into megabytes per second (MB/s) do the following:

Realize that there are 8 bits to a byte
So: (1,000,000 bits) / (8 bits / 1 byte) = 125,000 bytes/s (Bps)

Now suppose we are given the speed of a storage device in Mbps, take whatever Mbps you are given, multiply it by 125,000 to get the total Bps

Supposing we have 1.5Mbps:
1.5 * 125,000 = 187,500 Bps

Convert this to MB/s we devide by 1K (1024 bytes) to get in KB/s and then by another 1024 bytes to get MB/s:
(187,500 / 1024) / 1024 = .18MB/s

Happy converting. But really. This is very important when you go shoping around for a great deal on storage equipment. There is no way you would pay the same amount of monies for a USB 1.x device as a USB 2.0 device. There are just magnitude differences in speed.

For additional information on data rates