Data Storage Converter
Convert between decimal (SI) and binary (IEC) storage units
All Conversions
| Unit | Value |
|---|---|
| Bits (b) | 4,000,000,000,000 |
| Bytes (B) | 500,000,000,000 |
| Kilobytes (KB) | 500,000,000 |
| Megabytes (MB) | 500,000 |
| Gigabytes (GB) | 500 |
| Terabytes (TB) | 0.500000 |
| Petabytes (PB) | 0.000500000 |
| Kibibytes (KiB) | 488,281,250 |
| Mebibytes (MiB) | 476,837.158203 |
| Gibibytes (GiB) | 465.661287 |
| Tebibytes (TiB) | 0.454747 |
| Pebibytes (PiB) | 0.000444089 |
Decimal vs Binary Storage Units
There are two systems for measuring digital storage: decimal (SI) and binary (IEC). This dual system is the primary reason why your hard drive appears smaller in your operating system than what the manufacturer advertises.
The Two Systems
| Decimal (SI) | Binary (IEC) | Difference |
|---|---|---|
| 1 KB = 1,000 B | 1 KiB = 1,024 B | 2.4% |
| 1 MB = 1,000,000 B | 1 MiB = 1,048,576 B | 4.9% |
| 1 GB = 1,000,000,000 B | 1 GiB = 1,073,741,824 B | 7.4% |
| 1 TB = 10¹² B | 1 TiB = 2⁴⁰ B | 10.0% |
Hard drive manufacturers use decimal (SI) units because they result in larger numbers. Operating systems (Windows, macOS, Linux) historically display sizes in binary units but label them with SI prefixes (showing "GB" when they mean "GiB"). This creates the confusing situation where a "1 TB" drive shows as "931 GB" in Windows.
Real-World Examples
| Advertised | Shown in OS | "Missing" |
|---|---|---|
| 256 GB SSD | 238 GiB | 18 GiB |
| 500 GB HDD | 465 GiB | 35 GiB |
| 1 TB SSD | 931 GiB | 69 GiB |
| 2 TB HDD | 1.82 TiB | 138 GiB |
Frequently Asked Questions
Why does my 1 TB hard drive show as 931 GB?
Hard drive manufacturers use decimal units (1 TB = 1,000,000,000,000 bytes), but Windows displays sizes in binary units labeled as 'GB' (actually GiB, where 1 GiB = 1,073,741,824 bytes). When you divide 1,000,000,000,000 by 1,073,741,824, you get approximately 931 GiB. The space isn't missing — it's just measured differently.
What's the difference between GB and GiB?
GB (gigabyte) is a decimal unit where 1 GB = 1,000,000,000 bytes (10⁹). GiB (gibibyte) is a binary unit where 1 GiB = 1,073,741,824 bytes (2³⁰). The difference is about 7.4%. Storage manufacturers use GB, while operating systems often use GiB internally.
Which system should I use?
Use decimal (SI) units when discussing storage capacity as advertised by manufacturers or when communicating with non-technical users. Use binary (IEC) units when working with operating systems, programming, or when precision matters. In technical documentation, the IEC units (KiB, MiB, GiB) are preferred because they are unambiguous.
How many bytes are in a kilobyte?
It depends on the context. In the decimal (SI) system, 1 KB = 1,000 bytes. In the binary system, 1 KiB (kibibyte) = 1,024 bytes. Historically, 'kilobyte' was used for both, which caused confusion. The IEC introduced the 'kibibyte' (KiB) in 1998 to resolve this ambiguity.