Data Storage Converter

KB, MB, GB — and why your files never quite add up

Few unit conversions cause as much everyday confusion as digital storage. You buy a "1TB" hard drive, plug it in, and your computer reports something closer to 931GB available. That's not a manufacturing defect — it's two different, both legitimate, definitions of the same prefixes colliding. This tool lets you convert using either the decimal (SI, base-1000) system that storage manufacturers use, or the binary (base-1024) system that operating systems typically use for reporting free space, so you can see exactly where the "missing" storage went.

Decimal versus binary units

In the decimal system, a kilobyte (KB) is exactly 1,000 bytes, a megabyte (MB) is 1,000 kilobytes, and so on — the same clean base-10 scaling used for every other metric unit, and the convention storage manufacturers use on product packaging. In the binary system, formalised with the kibibyte (KiB), mebibyte (MiB), gibibyte (GiB), and tebibyte (TiB) prefixes, each step is a multiple of 1,024 (2¹⁰), matching how computers actually address memory in powers of two. Windows and some other operating systems have historically labelled binary-based figures with decimal prefix names (calling 1,073,741,824 bytes "1GB" when it's technically 1GiB), which is the root cause of the "missing storage" confusion — this tool includes both prefix families explicitly labelled so you can convert accurately regardless of which convention a specific product or piece of software is using.

Practical examples

A "500GB" drive as advertised (decimal) actually holds about 465.7GiB as reported by an operating system using binary counting — the drive isn't missing storage, it's just being measured two different ways. Video editors and photographers calculating whether raw footage will fit on a memory card, developers estimating cloud storage or bandwidth costs billed in decimal gigabytes, and IT staff reconciling "advertised" versus "reported" capacity across a fleet of devices all rely on understanding — and converting between — both systems.

Bits versus bytes

The tool also includes bits, the smallest unit, where 8 bits make 1 byte. This distinction matters most when discussing network speeds: internet plans are usually advertised in megabits per second (Mbps), while file sizes are measured in megabytes (MB) — so a "100 Mbps" connection downloads at a theoretical maximum of about 12.5 MB per second, not 100MB. Confusing bits and bytes is one of the most common sources of "why is my download slower than my internet plan says it should be" confusion, and this converter makes the eightfold difference easy to check.

Using the tool well

When comparing a purchased storage device's advertised capacity to what your operating system reports, always convert the advertised (usually decimal) figure into the binary unit your OS uses (GiB, TiB) rather than assuming they're interchangeable — that single step resolves almost all "my drive is smaller than advertised" confusion. For network speed calculations, remember the eight-to-one bit-to-byte ratio before comparing an ISP's advertised speed to a file's download time.

Checking software and firmware requirements

Software system requirements sometimes mix decimal and binary units without labelling which is which — if a download or installer reports a size that doesn't match the "required space" figure on a product page, converting both into the same prefix family first is a quick way to confirm whether it's a genuine shortfall or just a unit-labelling inconsistency.