Gigabyte – an ex­plan­a­tion of the data storage unit

There are many different units of in­form­a­tion that measure data storage ca­pa­cit­ies, i.e., the storage capacity of a hard disk or the size of a file. One of the best-known units of meas­ure­ment is the gigabyte, which we tend to encounter regularly – be it when buying a new USB stick, a memory card for a smart­phone, or when choosing the data volume of a new mobile phone contract. But what’s actually in a gigabyte; how large is it in practice, and how can you convert it to other units such as megabyte or terabyte?

A gigabyte (GB) is a fre­quently used standard unit in in­form­a­tion tech­no­logy that provides in­form­a­tion about the storage capacity of a medium or the size of a file. GB is also used for mobile phone tariffs to indicate the monthly data volume included in a mobile phone contract. To classify the term gigabyte correctly, it’s worth un­der­stand­ing what the unit of meas­ure­ment consists of and how it relates to other data storage units.

One gigabyte is equal to around one billion bytes, with one byte rep­res­ent­ing the smallest data quantity in digital tech­no­logy. In practice, a byte rep­res­ents a single letter. The byte comprises 8 bits, so-called ‘binary digits’. The bit is the smallest unit of in­form­a­tion that binary com­mu­nic­a­tion by computers is built on. Since computers always process more than one bit for data storage or data trans­mis­sion, bits are sum­mar­ised in bytes.

Nearly as common as gigabytes are meas­ure­ments in megabytes and terabytes. According to the decimal system, 1,000 MB = 1 GB and 1,000 GB = 1 TB. However, this con­ver­sion has its pitfalls: Computers use the binary system (or dual system), which is based on only two digits and is therefore based on base 2 (2^x). The SI prefixes mega, giga, and tera originate from the decimal system, which is based on base 10 (10^x), since a total of ten digits are being used.

When you convert bytes using the number 1,000, de­vi­ations arise and as data quant­it­ies grow, these de­vi­ations also become ever larger making for imprecise meas­ure­ments. That is why the In­ter­na­tion­al Elec­tro­tech­nic­al Com­mis­sion (IEC) in­tro­duced new prefixes based on the power of 2. The revised units of meas­ure­ment are called binary prefixes or IEC prefixes. They are based on the SI prefixes but contain the in­ter­me­di­ate syllable ‘bi’. Since the con­ver­sion number 1,024 is used in the system, 1 gibibyte = 1,024 mebibytes and 1 tebibyte = 1,024 gibibytes.

Although these meas­ure­ment units are also re­com­men­ded by the In­ter­na­tion­al Bureau of Weights and Measures (BIPM), they have yet to catch on. Instead, the con­ver­sion number 1,024 is used alongside existing terms mega, giga, and tera.

Megabytes, gigabytes, and terabytes are the units of in­form­a­tion, you’re likely to encounter most fre­quently when using digital media. The table below sum­mar­ises different units used globally, the number of bytes they contain, and how they are related to each other.

The units of meas­ure­ment displayed in the table are quite abstract. To give you a better idea of the amount of data each unit can store, here are a few examples:

Storage ca­pa­cit­ies:

1 KB = a text with approx. 1,000 letters

1 MB = approx. 400 pages in a book

1 GB = approx. 250 MP3 songs in medium quality

1 TB = approx. 250 down­loaded movies

Data usage:

Approx. 10 KB = Sending a message in WhatsApp

Approx. 10–30 MB = a one-minute YouTube video in HD quality

Approx. 1 GB = 5 hours of video streaming in standard defin­i­tion.

Since when has the gigabyte been used and what for?

Until the early 1980s, a size spe­cific­a­tion in megabytes was suf­fi­cient for storage media. With in­creas­ing ca­pa­cit­ies, however, megabytes have been replaced by the next largest unit of meas­ure­ment – the gigabyte. In 1980, IBM released the first 1.28 GB hard drive that was the size of a re­fri­ger­at­or. It took 10 years before the first computers with 1 GB drives became com­mer­cially available. Thanks to ongoing tech­no­lo­gic­al advances, terabytes or even petabytes have become more common units of meas­ure­ment for hard disk drives.

Gigabytes are far from being obsolete. Today, GB is used to indicate file sizes or the storage capacity of USB sticks, external hard drives, CD-ROMs, or DVDs. Com­mer­cially available memory cards in smart­phones or tablets usually have a storage capacity of 16, 32, or 64 GB. Mobile phone providers indicate con­trac­tu­ally guar­an­teed, monthly data volumes in GB. Cloud providers tend to use this unit to calculate the costs incurred for their storage ca­pa­cit­ies (e.g., in the form of cents per gigabyte).