Data Storage Converter
Storage is the one unit system where two definitions compete: drive makers use decimal (1 GB = 1,000,000,000 bytes) while operating systems use binary (1 GiB = 1,073,741,824 bytes). This converter shows both, so a "1 TB" drive reporting 931 GB stops being a mystery.
Last updated — conversions use exact unit definitions, so results stay accurate.
| Unit | Value |
|---|
How it works
Two naming systems overlap here, and mixing them is why your new drive looks smaller than advertised. Decimal units follow SI: 1 KB is 1,000 bytes, 1 MB is 1,000,000 bytes, 1 GB is 1,000,000,000 bytes. Drive manufacturers and network speeds use these.
Binary units use powers of 1,024 and were formally named kibibytes, mebibytes, gibibytes and tebibytes in 1998 to remove the ambiguity. Windows and most operating systems use them while still printing the older "GB" label, which is the root of the confusion.
The practical effect: a drive sold as 1 TB holds 1,000,000,000,000 bytes. Divide that by 1,073,741,824 and you get 931 GiB — which Windows displays as "931 GB". Nothing is missing; the number is the same, only the unit differs. The gap grows with size: about 2.4% at gigabyte scale and 9.1% at terabyte scale.
Bits and bytes are also routinely confused. A byte is 8 bits. Network speeds are advertised in bits (a 100 Mbps connection) while file sizes and download progress are shown in bytes, so a 100 Mbps line downloads at about 12.5 MB/s. That factor of 8 explains most "my internet is slower than promised" complaints.
Decimal vs binary at a glance
| Decimal (SI) | Bytes | Binary (IEC) | Bytes | Difference |
|---|---|---|---|---|
| 1 kilobyte (KB) | 1,000 | 1 kibibyte (KiB) | 1,024 | 2.4% |
| 1 megabyte (MB) | 1,000,000 | 1 mebibyte (MiB) | 1,048,576 | 4.9% |
| 1 gigabyte (GB) | 1,000,000,000 | 1 gibibyte (GiB) | 1,073,741,824 | 7.4% |
| 1 terabyte (TB) | 1,000,000,000,000 | 1 tebibyte (TiB) | 1,099,511,627,776 | 10.0% |
Frequently asked questions
Why does my 1 TB drive only show 931 GB?
Because the manufacturer counts a terabyte as 1,000,000,000,000 bytes (decimal) while your operating system divides by 1,073,741,824 and labels the result GB. 1,000,000,000,000 ÷ 1,073,741,824 = 931 GiB. No capacity is missing — the two systems simply use different definitions.
What is the difference between MB and MiB?
MB is decimal: 1,000,000 bytes. MiB (mebibyte) is binary: 1,048,576 bytes, or 1,024 × 1,024. The IEC introduced the "bi" names in 1998 to end the ambiguity, but Windows and many apps still print MiB values with an MB label.
How many megabytes are in a gigabyte?
Decimal: 1,000 MB in 1 GB. Binary: 1,024 MiB in 1 GiB. Most storage marketing uses the decimal figure, which is why a "1 GB" file and a "1 GiB" file differ by about 74 MB.
What is the difference between a bit and a byte?
A byte is 8 bits. Bits are used for data transfer rates (Mbps) and bytes for file sizes (MB). A 100 Mbps connection therefore downloads at about 12.5 MB/s — the factor of 8 accounts for most apparent speed shortfalls.
How long does it take to transfer 1 TB?
Divide the size by the transfer rate, remembering that rates are quoted in bits. On a 1 Gbps connection, 1 TB takes roughly 2 hours 13 minutes at theoretical maximum: 8,000,000,000,000 bits ÷ 1,000,000,000 bps ≈ 8,000 seconds. Real-world overhead usually adds 10–20%.