Byte/Bit Converter

This tool converts between the units used to measure digital data: bits and bytes, and their kilo, mega, giga, tera, peta and exa multiples in both forms. Enter a number, choose what it is and what you want, and read the answer. It is the fastest way to settle questions like how many megabytes are in a 4.7 GB disc image, or what a 25 Mbps connection means in megabytes per second.

The one thing worth knowing before you start is that there are two different meanings of "kilobyte" in circulation, and the gap between them is the source of nearly every confusing number in computing.

Bits or bytes — which one am I looking at?

A bit is a single binary digit. A byte is eight of them. The abbreviations differ only by capitalisation, which is unhelpful but universal:

• b (lower case) means bits — Kb, Mb, Gb
• B (upper case) means bytes — KB, MB, GB

The rule of thumb: network speeds are quoted in bits, file sizes in bytes. An internet plan sold as 25 Mbps delivers 25 ÷ 8 = 3.125 megabytes per second at best. That is not the provider cheating; it is two different units that happen to share a letter.

Why does a 1 TB drive show up as 931 GB?

Because the manufacturer and the operating system are using different definitions of "giga".

Drive makers use decimal SI prefixes, where each step is a factor of 1,000. Windows reports capacity using binary multiples, where each step is a factor of 1,024, but labels them with the decimal names anyway. So a drive sold as 1 TB really does hold 1,000,000,000,000 bytes, and Windows divides that by 1,024 three times:

• 1,000,000,000,000 ÷ 1,024 ÷ 1,024 ÷ 1,024 = 931.3

Nothing is missing. The drive is the size it says it is; the figure on screen is measured with a different ruler. The correct names for the binary units are kibibyte (KiB), mebibyte (MiB) and gibibyte (GiB) — one GiB is 1,073,741,824 bytes — but they never caught on outside standards documents.

This converter uses decimal multiples, matching how storage and bandwidth are actually sold and how file sizes are labelled on most platforms.

A worked example: sizing a download

A dual-layer DVD image is 8.5 GB. You want to know how long it takes on a 50 Mbps connection.

1. Convert the file to bits: 8.5 × 1,000,000,000 × 8 = 68,000,000,000 bits.
2. Divide by the line rate: 68,000,000,000 ÷ 50,000,000 = 1,360 seconds.
3. That is about 22 minutes 40 seconds at the full advertised rate.

Real transfers run slower because of protocol overhead and contention, so treat that as a floor rather than a promise.

How to use the converter

1. Type the value you already have into the input box.
2. Select its unit from the first dropdown — check the capital B carefully.
3. Select the unit you want in the second dropdown.
4. The converted figure appears immediately, and you can copy it straight out.

Where these conversions actually come up

Working out whether a video will fit in an email attachment limit. Checking that a backup set fits the destination volume. Translating a hosting plan's monthly transfer allowance into how many page views it covers. Reading a log file that reports sizes in bytes when you think in megabytes. Sizing a database column, where the difference between kilobytes and kibibytes decides whether a row fits a page boundary.

In each case the arithmetic is trivial and the unit confusion is not, which is exactly the sort of job worth handing to a calculator.

Frequently asked questions

Is a kilobyte 1,000 or 1,024 bytes?

Both are in use. Strictly, a kilobyte is 1,000 bytes and 1,024 bytes is a kibibyte. In practice operating systems and older software often say kilobyte and mean 1,024. This tool uses 1,000.

How many megabytes are in a gigabyte?

1,000 in decimal terms, which is what this converter and most storage labelling use. If you are working with a system that reports in binary multiples, the answer is 1,024.

Why are internet speeds advertised in bits?

Historical convention from telecommunications, where data has always been counted as a stream of bits on a line rather than as files. It also produces a larger number, which no marketing department has ever objected to.

What comes after a terabyte?

Petabyte (1,000 TB), then exabyte (1,000 PB). Beyond that are zettabytes and yottabytes, which are currently only used for talking about global data volumes rather than anything you can buy.

Does this tool handle bits and bytes in the same conversion?

Yes. You can convert gigabits to megabytes directly; the factor of eight is applied along with the prefix change, so you do not have to do it as two steps.

Related tools

• Base64 Encode/Decode — encoding inflates data size by roughly a third, which this helps you measure.
• Text to Binary — see the individual bits behind a string.
• Image Compressor — reduce file sizes once you know the budget you are working to.
• Binary to Decimal — for when the numbers themselves need converting.