Byte (B), kilobyte (kB), megabyte (MB), gigabyte (GB), terabyte (TB) and petabyte (PB)

1 Byte (B) = 8 bits (b) which can describe 256 discrete values (brightness, color, etc.).

Traditionally, just as computer-folk like to start counting from zero, they also ascribe 2 raised to the power 10, 20, 30, etc. (210, 220, 230, etc.) to the values kilo, mega, giga, etc. which become, 1,024, 1,048,576, 1,073,741,824, etc. To be factually correct, these powers of 2 should actually be called kibibyte (KiB), mebibyte (MiB), gibibyte (Gib), tebibyte (TiB) etc., though this is not very commonly seen in practice.

This can be difficult to handle for those drilled only in base-10 mathematics. Fortunately, disk drive manufacturers, who have to deal in increasingly vast numbers, describe their storage capacity in powers of 10, so a 100 GB drive has 100,000,000,000 bytes capacity. Observation suggests both systems are continuing in use…which could lead to some confusion.

TraditionalNewApprox Duration 
1 kB = 210 bytes = 1,024 B103 B2/3 line1/5 line1/8 line
1 MB = 220 bytes = 1,048,576 B 106 B1 frame1/5 frame130 lines
1 GB = 230 bytes = 1.074 x 109 B109 B47 sec6.4 sec3.5 sec
1 TB = 240 bytes = 1.099 x 1012 B1012 B13¼ hrs1¾ hrs58 mins
1 PB = 250 bytes = 1.126 x 1015 B1015 B550 days74 days40 days

Currently 3.5-inch hard disk drives store from about 100 GB to 6 TB. Solid-state store chips, RAMs, increment fourfold in capacity every generation now offering up to 8Gb chips (i.e. 8 x 230). Flash memory is now widely used in many professional and consumer video cameras.

A full frame of standard definition digital television, sampled at 10 bits according to ITU-R BT.601, requires around 1 MB of storage (1.037 MB for 576-line, 876 kB for 480-line systems). HDTV frames comprise up to 5 or 6 times more data, and 2K digital film frames sampled in RGB or X´Y´Z´ (DCI colorspace) are about 12 MB. 4K quadruples that to 48 MB. Storing the larger formats as uncompressed or applying ‘lossless’ compression makes huge demands on resources.

See also: DCI, DRAM, Disk drives, Storage