Data Storage Converter
Convert between bytes, kilobytes, megabytes, gigabytes and terabytes — with decimal and binary units kept separate.
How to use this calculator
- 1Enter the value you want to convert.
- 2Pick the unit you are converting from and the one you want.
- 3The table below shows the same value in every other supported unit.
How the calculation works
result = (value × factor(from) ) / factor(to)- factor
- How many bytes one unit represents
Every value is converted to bytes first, then out to the target unit. This means n units need n factors rather than n² conversion pairs.
Decimal units (kB, MB, GB) are powers of 1,000. Binary units (KiB, MiB, GiB) are powers of 1,024. They are genuinely different quantities, and the gap widens at each step — 7.4% at gigabyte scale, 10% at terabyte scale.
Storage manufacturers use decimal units; Windows reports binary units while labelling them "GB". That discrepancy, not missing space, is why a new 500 GB drive appears as roughly 465 GB in Windows.
Network speeds are quoted in bits per second, storage in bytes. Dividing by eight converts between them.
Worked example
500 gigabytes (1000 mb) to gibibytes (1024 mib)
- 1.One gigabytes (1000 mb) is 1,000,000,000 bytes, so 500 GB is 500,000,000,000 bytes.
- 2.One gibibytes (1024 mib) is 1,073,741,824 bytes, so divide: 500,000,000,000 ÷ 1,073,741,824 = 465.66129.
- 3.Put another way, 1 GB = 0.9313226 GiB.
Result: 465.66129 GiB
What a byte actually is
A bit is the smallest unit of digital information — a single binary 0 or 1. A byte groups eight bits together, which is enough to represent 256 distinct values, historically enough to encode one character of text. Every larger unit of data storage, from kilobytes to petabytes, is just some multiple of that same basic byte.
Where things get complicated is exactly what multiple. Computers are built on binary logic, so the natural "round numbers" inside a computer are powers of two — 1,024 rather than 1,000. But the prefixes kilo-, mega- and giga- come from the metric system, where they have always meant exactly 1,000 and 1,000,000. Data storage inherited both conventions at once, and for decades used the same prefix for both, which is the root of most confusion around file sizes.
Two genuinely different sets of units
To resolve the ambiguity, the industry eventually introduced a separate set of binary prefixes, though adoption has been slow and inconsistent.
- Decimal (SI) units — kilobyte, megabyte, gigabyte, terabyte — powers of 1,000, matching how every other metric prefix works. This is what storage manufacturers use on packaging and spec sheets for hard drives, SSDs and USB sticks.
- Binary (IEC) units — kibibyte, mebibyte, gibibyte, tebibyte — powers of 1,024, introduced in 1998 by the International Electrotechnical Commission specifically to give the binary meaning its own unambiguous name instead of overloading the metric one.
- What operating systems actually show — Windows historically calculates in binary (1,024-based) but labels the result with decimal unit names like "GB" — which is the single biggest source of the "my drive is missing space" complaint. macOS and most Linux file managers now report true decimal units and label them correctly.
Why a "500 GB" drive shows less than 500 GB
A drive manufacturer selling a "500 GB" drive means exactly 500,000,000,000 bytes — the correct decimal definition of a gigabyte. When that drive is plugged into a Windows PC, the operating system divides its byte count by 1,024 three times to compute a figure it displays as "GB," even though what it just calculated is actually GiB. The result is a number around 465, which looks like 35 GB of missing capacity but is really just two different definitions of the same unit label colliding.
The gap between decimal and binary units is not fixed — it grows at each step up the scale: about 2.4% at the kilobyte level, 4.9% at megabyte, 7.4% at gigabyte, and nearly 10% at terabyte. That widening gap is exactly why the discrepancy became impossible to ignore once terabyte-class drives became common.
Bits versus bytes — the other everyday mix-up
Network and internet connection speeds are conventionally advertised in bits per second (Mbps, Gbps), while file sizes and download progress bars are shown in bytes (MB, GB). Since there are eight bits in a byte, a "100 Mbps" internet connection tops out at roughly 12.5 MB/s of actual download throughput, not 100 MB/s — a mismatch that catches almost everyone off guard the first time they compare an advertised connection speed to an actual download speed.
Common conversion pitfalls
Keep these distinctions in mind when the numbers do not seem to add up.
- GB and GiB are not interchangeable — they differ by about 7.4%, and mixing them up is the most common cause of "missing" storage space complaints.
- Mbps and MB/s look similar but differ by a factor of eight — always check whether a speed figure is quoted in bits or bytes before comparing it to a file size.
- RAM is usually specified in true binary units — memory capacity (like "16 GB" of RAM) is conventionally a binary count even though it uses the decimal-looking label, unlike storage drives, which use true decimal counts — a subtle but real difference between the two contexts.
What this assumes, and where it stops
Assumptions
- Conversion factors follow the internationally agreed definitions of each unit.
Limitations
- Results are computed in double-precision floating point, which is exact to about 15 significant figures.
- Very large or very small values are displayed in scientific notation to avoid misleading precision.
Common questions
Why does my 1 TB drive show as 931 GB?
The manufacturer sells 1 TB meaning 1,000,000,000,000 bytes. Windows divides by 1,024 three times and calls the result "GB" when it is really GiB, giving 931. No space is missing — the two are just using different definitions of the same word. macOS and Linux report decimal units and show the full 1 TB.
What is the difference between MB and MiB?
A megabyte (MB) is 1,000,000 bytes; a mebibyte (MiB) is 1,048,576 bytes — about 4.9% more. The IEC introduced the binary prefixes in 1998 specifically to end this ambiguity, though adoption remains inconsistent.
Why is my 100 Mbps connection not downloading at 100 MB/s?
Because Mbps is megabits per second and MB/s is megabytes per second. There are eight bits in a byte, so 100 Mbps is at most 12.5 MB/s before protocol overhead. The factor of eight accounts for almost the entire apparent shortfall.
Sources
- Prefixes for binary multiples — US NIST
Formula and content last reviewed on .
Results are estimates for information only, not professional advice.
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