How it’s calculated
SI prefixes are powers of 10, so 1 kB = 1,000 bytes. Binary prefixes standardized by the IEC are powers of 2: 1 KiB = 1,024 bytes. Drive makers use decimal units; many operating systems report binary units, often still labeled "GB".
Example: a 1 TB drive holds 10¹² bytes ÷ 1,073,741,824 = 931.32 GiB, which is why it shows as about "931 GB" in Windows.
Frequently asked questions
Why does my 1 TB drive show only 931 GB?
The drive is sold as 1,000,000,000,000 bytes (decimal TB). Windows divides by 1,073,741,824 (a GiB) but labels the result "GB", so it shows about 931. No space is missing.
How many MB are in a GB?
In decimal units, 1,000 MB = 1 GB. In binary units, 1,024 MiB = 1 GiB.
What is the difference between bits and bytes?
A byte is 8 bits. Network speeds are usually quoted in bits per second (Mbps) and file sizes in bytes (MB), so 100 Mbps moves at most 12.5 MB per second.
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Sources
- Prefixes for binary multiples — U.S. National Institute of Standards and Technology
- The International System of Units (SI Brochure) — BIPM
Formulas are taken from the free public references above. Results are provided “as is” for informational and educational purposes only. See our disclaimer.
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