What is a bit? Bits and bytes explained

Bits and bytes are part of our everyday digital life. Knowing about bits is essential for understanding how much storage your hard drive has or how fast your DSL connection is. So what is a bit and how is it different from a byte? A bit is the smallest unit of electronic information; multiple bits form a byte. Whereas the storage capacity of hard drives is given in bytes, data transfer rates are shown in bits. Keep reading to find out more about what bits and bytes really mean.

You’re probably familiar with the image of green ones and zeros filling the screen, made famous by the Matrix movies. This binary code forms the basis for all digital information processing and data transfers. Computers use binary numbers to communicate. Binary numbers represent two states: 1 for “on/true” and 0 for “off/false”. The bit is the representation of one of these two states.

“Bit” stands for binary digit and is the smallest unit of binary information. It thus forms the basis for all larger data in digital technology. It doesn’t get smaller than a bit, as a bit represents the state 0 or 1. Since computers communicate using binary states, they don’t understand anything “smaller” than 1 or 0. Figuratively speaking, the bit is the smallest possible container in which information can be stored.

Thanks to their very similar names, bits and bytes can easily be confused. Bits are primarily used to represent data use and transmission speeds of internet, telephone, and streaming services. The bit rate refers to how many bits are transmitted per second.

Bytes, on the other hand, are used to express storage sizes. 1 byte is equal to 8 bits. This means that one byte can represent 256 (2⁸) different states. A byte is usually the smallest unit that can represent a letter of the alphabet, for example. The kilobyte is the next largest unit; it equals 1,024 bytes and can represent 10³ states.

Bits and bytes are too small to be used in most situations. Instead, various multiples are commonly used. DSL providers usually advertise high-speed internet connections with 300 megabits per second (Mbit/s). And the storage capacities of hard drives or USB sticks are usually given in megabytes, gigabytes, or terabytes.

The following table provides an overview of bit and byte multiples:

The following bit rates are often used when talking about data transmission or the reading/writing speeds of hardware and storage devices:

1. Kbit/s: Kilobits per second
2. Mbit/s: Megabits per second
3. Gbit/s: Gigabits per second
4. Tbit/s: Terabits per second

Terms like “gigabytes” and “terabytes” can be hard to grasp. To get an idea of what these data quantities actually mean, take a look at these concrete examples:

Storage capacity:

1 MB = approx. 1 book

1 GB = approx. 3,334 books

1 TB = approx. 3,334,000 books

Data use:

approx. 100–200 KB = 1 image in a messenger app

approx. 100–200 MB = 1 hour-long video call

approx. 300 GB = 100 hours of video streaming

The term “bit” was first used by John W. Turkey, an American mathematician. Turkey shortened “binary information digit” into “bit” in a Bell Labs memo. The word became more widely used after Claude E. Shannon included it in his 1948 treatise “A Mathematical Theory of Communication”. Vannevar Bush used the phrase “bits of information” to refer to truth values that used to be saved on computer punch cards.