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 |
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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.
How much storage does a 4K movie take up?
A typical 4K Ultra HD movie takes up 50-100 GB depending on length and compression. A 2-hour 4K Blu-ray rip averages about 60-80 GB. Streaming services use heavy compression, so a 4K stream uses about 7 GB per hour. On a 1 TB drive (931 usable GiB), you could store roughly 12-15 uncompressed 4K movies.
Why do SSDs show less capacity than advertised?
SSDs show less capacity for two reasons: First, the decimal vs binary measurement difference (same as HDDs). Second, SSDs reserve a portion of their capacity for over-provisioning — extra space used for wear leveling, garbage collection, and maintaining performance. This reserved space is typically 7-28% depending on the drive model.
What is the largest unit of data storage?
The largest commonly used unit is the yottabyte (YB), which equals 1 trillion terabytes or 10²⁴ bytes. However, in practice, the largest units you will encounter are petabytes (PB) in enterprise data centers and exabytes (EB) when discussing global data volumes. As of 2024, the total amount of data in the world is estimated at around 120 zettabytes.