Kilobyte

Key takeaways

Kilobyte belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Kilobyte to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Kilobyte from memory before moving on to harder problems.

Reference excerpt

The kilobyte is a multiple of the unit byte for digital information. The International System of Units (SI) defines the prefix kilo as a multiplication factor of 1000 (103); therefore, one kilobyte is 1000 bytes. The internationally recommended unit symbol for the kilobyte is kB. In some areas of information technology, particularly in reference to random-access memory capacity, kilobyte instead often refers to 1024 (210) bytes. This arises from the prevalence of sizes that are powers of two in modern digital memory architectures, coupled with the coincidence that 210 differs from 103 by 2.4%. The kibibyte is defined as 1024 bytes, avoiding the ambiguity issues of the kilobyte.

Definitions and usage

Decimal (1000 bytes) In the International System of Units (SI) the metric prefix kilo means 1,000 (103); therefore, one kilobyte is 1000 bytes. The unit symbol is kB. This is the definition standardised by the International Electrotechnical Commission (IEC). This definition, and the related definitions of the prefixes mega (1,000,000), giga (1,000,000,000), etc., are most commonly used for data transfer rates in computer networks, internal bus, hard drive and flash media transfer speeds, and for the capacities of most storage media, particularly hard disk drives, flash-based storage, and DVDs. It is also consistent with the other uses of the metric prefixes in computing, such as CPU clock speeds or measures of performance. The international standard IEC 80000-13 uses the term "byte" to mean eight bits (1 B = 8 bit). Therefore, 1 kB = 8000 bit. One thousand kilobytes (1000 kB) is equal to one megabyte (1 MB), where 1 MB is one million bytes.

Binary (1024 bytes) The term kilobyte has traditionally been used to refer to 1024 bytes (210 B). The usage of the metric prefix kilo for binary multiples arose as a convenience, because 1024 is approximately 1000. The binary interpretation of metric prefixes is still prominently used by the Microsoft Windows operating system. Binary interpretation is also used for random-access memory capacity, such as main memory and CPU cache size, due to the prevalent binary addressing of memory. The binary meaning of the kilobyte for 1024 bytes typically uses the symbol KB, with an uppercase letter K. The B is sometimes omitted in informal use. For example, a processor with 65,536 bytes of cache memory might be said to have "64 K" of cache. In this convention, one thousand and twenty-four kilobytes (1024 KB) is equal to one megabyte (1 MB), where 1 MB is 10242 bytes. In December 1998, the IEC addressed such multiple usages and definitions by creating prefixes such as kibi, mebi, gibi, etc., to unambiguously denote powers of 1024. Thus the kibibyte, symbol KiB, represents 210 bytes = 1024 bytes. These prefixes are now part of IEC 80000-13. The IEC further specified that the kilobyte should only be used to refer to 1000 bytes. The International System of Units restricts the use of the SI prefixes strictly to powers of 10.

Use of term The Shugart SA-400 51⁄4-inch floppy disk (1976) held 109,375 bytes unformatted, and was advertised as "110 Kbyte", using the 1000 convention. Likewise, the 8-inch DEC RX01 floppy (1975) held 256,256 bytes formatted, and was advertised as "256k". On the other hand, the Tandon 51⁄4-inch DD floppy format (1978) held 368,640 (which is 360×1024) bytes, but was advertised as "360 KB", following the 1024 convention. Early home computer systems would often advertise using the 1024 convention, hence the naming of the Commodore 64, Commodore 128, and the Amstrad CPC 464. On modern systems, all versions of Microsoft Windows divide by 1024 and represent a 65,536-byte file as "64 KB". Conversely, Mac OS X Snow Leopard and newer represent this as 66 kB, rounding to the nearest 1000 bytes; file sizes are reported with decimal prefixes. As of 2016, the binary interpretation was still used in marketing and billing by some telecommunication companies, such as Vodafone, AT&T, Orange and Telstra.

Data examples The Lord's Prayer, in Latin, is 296 bytes (about 0.3 kilobytes). The short story The Gift of the Magi, by O. Henry, hosted on Project Gutenberg as an uncompressed plain text file, is 11,203 characters; this is 11.2 kilobytes (dividing by 1,000) or 10.94 kibibytes (dividing by 1,024). The Cask of Amontillado, by Edgar Allan Poe, is 12,843 bytes (12.8 kilobytes or 12.5 kibibytes). The size of this article's wikitext source, as of August 2026, is 16.885 kilobytes. The novel The Picture of Dorian Gray, by Oscar Wilde, hosted on Project Gutenberg as an uncompressed plain text file, is 428,952 bytes; this is 428.95 kilobytes (428,952 divided by 1,000) and 418.90 kibibytes (divided by 1,024). Great Expectations is 994,639 bytes (994.639 kB), and Moby Dick is 1,191,763 bytes (1,191.763 kB).

Illustrations

Worked examples

Example 1 — a first encounter with Kilobyte

Start with the simplest possible case. Write down what Kilobyte claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Kilobyte before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Kilobyte ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Kilobyte

In research: Kilobyte appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Kilobyte in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Kilobyte is common in secondary-school and first-year university syllabi. It links to neighbouring topics Units of information, so understanding it makes those chapters shorter.
In everyday life: Look for Kilobyte outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Kilobyte in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kilobyte means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Kilobyte out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kilobyte in simple terms?

The kilobyte is a multiple of the unit byte for digital information. The International System of Units (SI) defines the prefix kilo as a multiplication factor of 1000 (103); therefore, one kilobyte is 1000 bytes.

Why does Kilobyte matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Kilobyte?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Kilobyte.