U
UseCalcForge Free Online Calculators
Tools
Publishing Science Developer Finance
 
Health Marketing Lifestyle All Tools
Contact Us
Developer Tools

Data Storage Converter.

Convert file and disk sizes across decimal and binary units, and see both readings of the same number of bytes.

Exact size in bytes

Decimal units — powers of 1000

Used by drive manufacturers, network speeds, and the SI standard.

Binary units — powers of 1024

What Windows, Linux, and most file managers actually display.

The advertised-versus-displayed gap

of decimal capacity is displayed by most operating systems as — a difference of . Nothing is lost; the two figures count the same bytes in differently sized units.

Runs entirely in your browser. The values you enter never leave your device — there is no request to our server and nothing is stored. How we handle data

Two Competing Definitions

Storage has two parallel unit systems, and almost every confusing size discrepancy traces back to something reported in one and read as the other.

Definitions

Decimal: 1 KB = 10³ = 1,000 bytes
Binary: 1 KiB = 2¹⁰ = 1,024 bytes
1 GB = 10⁹ bytes • 1 GiB = 2³⁰ bytes
Divergence ≈ 2.4% per unit step

The gap compounds with every step up the scale: 2.4% at kilobytes, 4.9% at megabytes, 7.4% at gigabytes, and 10% at terabytes. That is precisely why a 1 TB drive shows as roughly 931 GiB — the shortfall is not a hidden partition or a formatting overhead, it is the difference between dividing by 1000 three times and dividing by 1024 three times.

Who Uses Which

Knowing which convention a number came from is usually enough to resolve an apparent discrepancy.

Decimal — hardware and networks

Drive and SSD capacities, USB stick sizes, and mobile data allowances are all quoted in decimal units. Network speeds are decimal too, and measured in bits rather than bytes: a 100 Mbps link moves at most 12.5 MB per second.

Binary — operating systems

Windows File Explorer reports binary sizes while labelling them KB, MB, and GB, which is the single biggest source of confusion. Linux tools vary; ls -h uses binary while ls --si uses decimal. macOS switched to decimal in 2009, which is why the same drive reads differently on a Mac and a PC.

RAM is always binary

Memory is addressed in powers of two by physical design, so a 16 GB memory module really is 16 GiB — 17.18 billion bytes. Memory is the one place where the marketing figure and the binary figure genuinely agree.

Where the Difference Bites

Capacity planning is the main casualty. Provisioning storage for 500 GiB of data on a drive sold as 500 GB leaves you about 37 GiB short, and the mistake scales: at the petabyte level the two systems differ by more than 12%.

Transfer time estimates suffer from a related mix-up between bits and bytes. Divide a connection's advertised megabits per second by eight to get megabytes per second, then allow for protocol overhead of roughly 5-10% on top. A 1 GB file over a 100 Mbps line takes at least 80 seconds in theory and rather longer in practice.

Knowledge Base

Data Storage Units Methodology.

A byte is unambiguous; everything above it is not. Two standards define the prefixes — decimal powers of 1000 and binary powers of 1024 — and both are in daily use, often on the same screen, which is why converting sizes means naming the convention as well as the number.

The Calculation Branch

Decimal: KB = 10³, MB = 10⁶, GB = 10⁹, TB = 10¹², PB = 10¹⁵ bytes | Binary: KiB = 2¹⁰, MiB = 2²⁰, GiB = 2³⁰, TiB = 2⁴⁰, PiB = 2⁵⁰ bytes | 1 byte = 8 bits | Divergence at level n = (1 − (1000/1024)ⁿ) × 100%

Industrial Standards.

All conversions route through an exact byte count, so decimal and binary units are handled in the same pass and no rounding is applied until display. The IEC binary prefixes (kibi, mebi, gibi, tebi, pebi) are used for the 1024-based units, per IEC 60027-2 and ISO/IEC 80000-13. Values below 0.001 of a unit are shown in exponential notation rather than rounded to zero.

In-Depth Analysis & Reference Data

The binary prefixes were standardised by the IEC in 1998 specifically to end this ambiguity, but adoption has been patchy — largely because Windows continued to display binary values under decimal labels. Storage manufacturers were sued over the discrepancy in the United States during the 2000s and now include a footnote on packaging defining GB as one billion bytes.

Formatting overhead is a separate and much smaller effect that is often conflated with this one. A file system reserves space for its own metadata, journal, and allocation tables, typically a fraction of a percent to a few percent. If your drive is missing roughly 7% at the gigabyte level, that is the unit definitions; if it is missing a further sliver on top, that is the file system.

Registry Questions & FAQ.

Should I write MB or MiB in my own documentation?

Use MiB when you mean 1,048,576 bytes and MB when you mean 1,000,000. Being explicit costs one character and removes an entire category of misunderstanding, particularly in capacity planning and API documentation.

Why are network speeds in bits rather than bytes?

Because transmission is serial — bits go down the wire one at a time, so bits per second is the natural measure. Divide by 8 for bytes per second, and note that Mb and MB differ by a factor of eight, which is why a 100 Mbps connection downloads at about 12 MB/s.

All metrics verified against ISO/ASTM benchmarks.