What is a Data Size Converter?
A data size converter moves a quantity between the units used to measure digital information. There are two parallel systems, and confusing them is the source of nearly every surprise about storage capacity. The decimal system, from the International System of Units, uses steps of a thousand: a kilobyte is 1000 bytes, a megabyte a million and a gigabyte a billion. The binary system uses steps of 1024, because memory is addressed in powers of two, and its units are named with a middle syllable — kibibyte, mebibyte, gibibyte, abbreviated KiB, MiB and GiB.
The tool converts through bits, which is the common denominator all of these units share and also the unit network speeds are quoted in. A byte is eight bits, so a hundred-megabit connection delivers 100 million bits per second, which is 12.5 megabytes per second. That division by eight is why broadband speeds and download times never seem to agree, and it has nothing to do with the decimal-versus-binary question.
The figure that explains the missing capacity is at the top of the result: enter 1 TB and the tool reports the exact number of bytes, and what the operating system will call it. The drive is honestly labelled at a thousand billion bytes; Windows divides that by 1024 three times over and reports 931. The storage is all there. Which unit the operating system chooses to display is a matter of convention, not of lost space.
How to convert between data sizes
- Enter the number. Commas and spaces are ignored, so a figure copied out of a specification sheet works as-is.
- Choose the unit it is in, being careful about the middle syllable: kB is 1000 bytes and KiB is 1024.
- Read the whole table. Every other unit is shown at once, decimal and binary side by side, which makes the size of the difference obvious rather than theoretical.
- For a network speed, enter it in megabits or gigabits rather than megabytes — connection speeds are always quoted in bits.
- Use the exact byte count when the figure has to be precise, for example when checking a storage quota or a file size limit.
- Watch the drive comparison line when the input is a decimal unit of a gigabyte or more; that is the figure people are usually looking for.
Data Size Converter limits and rules
| Item | Limit |
|---|---|
| Units offered | Bit and the kilobit, megabit and gigabit steps; byte, kB, MB, GB, TB, PB; KiB, MiB, GiB, TiB, PiB |
| Conversion basis | Everything passes through bits, with one byte equal to eight bits |
| Decimal steps | 1000 — kB, MB, GB, TB are powers of ten |
| Binary steps | 1024 — KiB, MiB, GiB are powers of two |
| Precision | Six decimal places for ordinary values, exponential notation below 10⁻⁶ or above 10¹⁵ |
| Number handling | Standard double precision, which is exact for integers up to 2⁵³ ≈ 9 PB |
| Not covered | Rates per second, compression ratios and filesystem overhead |
When to use it
- Explaining to somebody why the 1 TB drive they bought shows less than a terabyte in File Explorer.
- Working out how long a file will take to download on a connection quoted in megabits per second.
- Checking whether a file will fit inside a hosting limit that is expressed in MiB while your file manager shows MB.
- Converting a memory figure for a configuration file where the value must be in kibibytes.
- Resolving an argument about whether a megabyte is a thousand kilobytes or 1024 of them — both answers are correct, in different systems.
Is it private?
The conversion is arithmetic in your browser, using a table of constants compiled into the page. Nothing is submitted, nothing is stored and there is no request to observe — the tool works with the network disconnected.
Frequently asked questions
Because the drive holds one trillion bytes, which is exactly what the manufacturer advertised, and the operating system reports that quantity in binary units while labelling them GB. Dividing a trillion by 1024 three times gives 931.3, so that is the figure Windows shows. No storage is missing and nothing is being hidden: the same amount of data is being described in two different units, one of which uses a name from the other system. macOS and Linux display decimal units by default, which is why the discrepancy is less visible there.
MB is a megabyte, a million bytes, defined by the SI prefixes that have meant powers of ten for two centuries. MiB is a mebibyte, 1,048,576 bytes, created by the IEC in 1998 so that the powers-of-two figures needed their own names. The difference is about five per cent at the megabyte level, seven per cent at the gigabyte and ten per cent at the terabyte, which is why the distinction only becomes noticeable as files get large. RAM is still quoted in binary units; storage is now quoted in decimal ones.
Because connection speeds are quoted in bits per second and download progress is measured in bytes. Dividing by eight converts between them: a 100 Mbps connection can transfer 12.5 MB per second at best, which is one gigabyte in about eighty-five seconds. Nothing is being lost, and the two figures were never in the same unit. This is a separate confusion from decimal against binary, and the two together are why advertisements and file managers appear to disagree by more than a factor of eight.
A thousand terabytes, or a million gigabytes, or about a thousand billion bytes. A single 4 TB drive holds roughly 0.004 of one, so a petabyte of storage means a rack rather than a box. Where the term appears in ordinary life it is usually in cloud billing or in retention policies, and at those sizes your provider's definition of the unit can differ from yours by ten per cent — which is worth checking before committing to a quota.
Usually in the decimal sense, but not always, and the distinction matters when a limit is enforced. Most hosting and mobile providers quote quotas in decimal units, in which case a gigabyte is a thousand million bytes. Some tooling measures in binary and calls the result GB anyway, which is how a 100 GB monthly allowance can run out a few per cent early. When the difference matters, check the units in the provider's own documentation rather than assuming.
Exact through the whole table for any value a person is likely to enter, because the arithmetic is multiplication and division by powers of ten and two on numbers well within the range where doubles represent integers precisely. Beyond roughly nine petabytes the underlying floating point arithmetic stops representing every integer, so the last digits of a very large figure are approximate. For a file size or a disk quota that ceiling is not something you will meet.
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Written and maintained by Md. Nur Hossain Repon.