The units of measurement in IT are components of the “International system of quantities” and defined by the “International Electrotechnical Commission” (IEC).

In measuring speeds and sizes, it can be confusing. For instance, doing a speedtest to the Internet, you might get readings such as 10Mbps or 1.25MBps. Although the former might look faster, it is actually the same speed as the latter. This is because a byte (B) consists of 8 bits(b) - 1.25million Bytes per second is the same as 10million bits per second(1.25 X 8 = 10). Always check the B vs b, divide or multiply by 8 to convert between Mbps and MBps. Bytes=Bits/8; Bits=BytesX8

More confusing can be GiB vs GB.

The Gigabyte (GB) is defined as 10⁹ bytes, i.e. 1 000 000 000 Bytes. However, the Gibibyte is defined as 1024³ which translates to 1 073 741 824 Bytes.

For e.g. you might buy a hard drive that is advertised as 500GB, but viewing the size in Windows it detects as 465GB, this is because the manufacturers actually mean 500 000 000 000 Bytes (GB) (multiples of 1000), but translating it to GiB (multiples of 1024) get you a value of 465GiB. It is the same amount of Bits and Bytes! Not all software indicates GB vs GiB correctly, which can add to the confusion. Traditionally, storage space is defined as GiB (hard disk space, RAM, etc) and data transmission and speeds (Internet and network transfers) are noted as GB.

 

1000Bytes=1KB	1024Bytes=1KiB
1000KB=1MB (1 000 000Bytes)	1024KiB=1MiB (1 048 576 Bytes)
1000MB=1GB (1 000 000 000Bytes)	1024MiB=1GiB (1 073 741 824 Bytes)
1000GB=1TB (1 000 000 000 000Bytes)	1024GiB=1TiB (1 099 511 627 776 Bytes)