# What is data transfer speed and how is it measured?

– Alex –

Speed measures how much data can be transfered in one second to your PC. It is rated in Kilo Bits per second, short Kbps. This can cause some confusion since the size of files is measured in Kilo Bytes. And when you download a web page or a file, your browser often indicates not Kilo Bits per second, Kbps (note the small letter “b”), but KBps, Kilo Bytes per second (note the capital letter “B”). To get a better feel for this, you need to understand that one Byte equals 8 Bits.

Example:

Assume you want to download some freeware from the Internet. The program file is 6 Mega Bytes. First, let’s translate that into Kilo Bits so that we can compare apples to apples. 1 Mega Byte is 1024 Kilo Byte. Therefore the file you want to download is 6144 Kilo Bytes big.

1 Mega Byte = 1024 Kilo Byte

6 Mega Bytes = 6144 Kilo Bytes (6 * 1024)

But since we want to measure in Kilo Bits, we still need to multiply this number by 8, since one Byte is 8 Bits.

6144 Kilo Bytes = 49152 Kilo Bit (6144 * 8)

Now that we figured that out, we can calculate how long it would take to download the file. Let’s say your transfer speed is 50 Kilo Bits per second (Kbps). We divide 49152 Kilo Bits by 50 Kilo Bits and get 983.

49152 Kilo Bits (File Size) / 50 Kilo Bits per second (Transfer Speed) = 983 seconds

This means it takes 983 seconds to transfer that file. In minutes, that would be 16.38.

983 seconds / 60 (60 seconds in a minute) = 16.38

In reality, it might take a little bit longer, since the data is not being transformed in one continuous stream but in little packets. The file is chopped up into small pieces, which are wrapped into packets, which are then individually sent one by one. The wrapper takes a few extra bits so that the information transfered is actually the total file size plus a few bytes extra for the packets.

– Alex –