Data storage converter
Storage capacity is measured in two systems — SI decimal (powers of 1000) and binary/IEC (powers of 1024). This converter handles both and shows the full conversion table.
| Unit | Value |
|---|
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How to use
- Enter a value.
- Pick the source unit (what you have).
- Pick the target unit (what you want).
- The result appears instantly, plus a full conversion table for every other unit.
Two measurement systems
Storage capacity is measured in two different ways, and they disagree by 2–10% depending on the size:
| SI unit | Value | Binary unit | Value |
|---|---|---|---|
| 1 KB | 1,000 B | 1 KiB | 1,024 B |
| 1 MB | 1,000,000 B | 1 MiB | 1,048,576 B |
| 1 GB | 10⁹ B | 1 GiB | 2³⁰ B |
| 1 TB | 10¹² B | 1 TiB | 2⁴⁰ B |
| 1 PB | 10¹⁵ B | 1 PiB | 2⁵⁰ B |
SI decimal (KB, MB, GB) uses powers of 1,000 — the standard SI prefix meaning. Used by hard drive manufacturers, network speeds, and almost all storage marketing.
Binary / IEC (KiB, MiB, GiB) uses powers of 1,024. Used by operating systems (Windows, macOS, Linux file managers), RAM manufacturers, and low-level programming. The “i” stands for binary.
Why a 1 TB drive shows as 931 GB
You buy a 1 TB hard drive. You plug it in. Windows says the capacity is 931 GB. Nothing is wrong — this is the SI-vs-binary disagreement:
- Marketing: 1 TB = 10¹² bytes = 1,000,000,000,000 bytes
- Windows: divides by 1,024³ and calls it “GB” even though it means GiB
- 10¹² / 2³⁰ = 931.3 GiB
At terabyte scale the gap is almost 7%. At the petabyte scale it’s nearly 11%.
Worked examples
Movie-sized file — 4 GB
- 4 GB = 4,000 MB = 4,000,000 KB = 4,000,000,000 bytes = 32,000,000,000 bits
- In binary units: 4 GB ≈ 3.725 GiB
iPhone storage — 256 GB
- 256 GB (advertised) = 256,000,000,000 bytes
- In the phone’s “Settings → About” screen: 238.4 GiB (divide by 2³⁰)
- Real usable space is lower still after the OS reserves a few gigabytes.
Notes
- Bits vs. bytes — network speeds are quoted in bits per second (Mbps, Gbps); file sizes in bytes (MB, GB). A 1 Gbps connection downloads at 125 MB/s, not 1 GB/s. Divide by 8.
- Capital B = byte, lowercase b = bit. Mbps ≠ MBps. A common source of confusion when reading internet speeds versus file sizes.
- RAM is typically sized in GiB (binary) because of how addressing works. Storage is typically sized in GB (decimal). The same “16 GB” label can mean either depending on the component.