Data Size Converter
Convert between bit, byte, KB, MB, GB, TB and PB — with both the decimal (1000-based) and binary (1024-based) interpretation shown at the same time.
How to use the data size converter
- Enter the value you want to convert.
- Choose the unit you're converting from and to.
- The result is shown automatically — both the decimal and binary interpretation, since they give a different answer.
Why does 1 GB give two different answers in MB?
There are two competing definitions of "kilo/mega/giga" for data sizes. Decimal (1000-based, SI standard) is used by hard drive and memory card manufacturers, as well as most network speeds — here 1 GB is exactly 1000 MB. Binary (1024-based) is how operating systems like Windows traditionally calculate and display disk space — here 1 GB is exactly 1024 MB.
This is the most common reason a "500 GB" drive shows less than 500 GB of free space in Windows: the drive is labeled using the decimal definition, but the operating system displays the space using the binary one.
Frequently asked questions
Why does Windows show less space than what's printed on the drive?
Because the drive is labeled using decimal GB (1000-based), while Windows displays free space in binary GB (1024-based). A drive labeled "500 GB" will therefore show around 465 GB in Windows — no space has actually disappeared, it's just two different ways of counting.
Which definition should I use?
It depends on what you're comparing. If you're talking about a file or a network speed from a manufacturer, it's often decimal (1000-based). If you're looking at what an operating system reports as free disk space or memory usage, it's often binary (1024-based).
How many bits are in a byte?
Always exactly 8 bits — this is a fixed definition and isn't affected by the decimal/binary question, which only applies to the units from KB upward.