Storage Unit Converter (GB, GiB, TB, bits)
Convert storage between bytes, kB–PB (decimal), KiB–PiB (binary) and bits, and see why a drive sold as 1 TB shows 931 GiB in the operating system.
The same amount of data in every decimal and binary unit, the best-fit figure for each, and the exact label-versus-OS shortfall percentage.
Example: 1 TB is 1,000,000,000,000 bytes = 931.32 GiB = 0.9095 TiB = 8 × 10¹² bits; a 256 GiB SSD is 274.88 GB. The label-to-OS shortfall at the terabyte order is 9.05 %.
A thousand,
or 1,024.
Why two unit systems exist, how the converter treats each, and what the shortfall percentage means.
Decimal and binary prefixes
The SI prefixes kilo, mega, giga, tera and peta mean powers of 1,000 — that is how drive and SSD capacities, network speeds and the metric system count. Memory, file systems and most operating systems count in powers of 1,024, for which IEC 80000-13 defines kibi, mebi, gibi, tebi and pebi (KiB, MiB, GiB, TiB, PiB). The converter turns your value into bytes with the exact factor of its unit and then divides by every other factor; nothing is rounded before display.
The missing gigabytes
A drive labelled 1 TB holds 10¹² bytes. Divided by 1,024³ that is 931.32 GiB, and an operating system that prints “GB” while counting in 1,024s shows exactly that figure. The shortfall grows with each order — 2.3 % at kilo, 4.6 % at mega, 6.9 % at giga, 9.05 % at tera, 11.2 % at peta — because (1000/1024)ⁿ shrinks with n. The percentage shown is for the order of the decimal label; no capacity is lost, and formatting overhead is a separate, smaller effect that this page does not estimate.
Bits
One byte is eight bits, and kbit, Mbit and Gbit use decimal prefixes as network equipment does — so 4 Gbit is 500 MB. For rates over time (Mbps to MB/s, data used per hour) use the Data Rate Converter. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- IEC 80000-13:2008 — prefixes for binary multiples (kibi, mebi, gibi, tebi, pebi)
- NIST SP 811 — SI prefixes and the byte; prefixes for binary multiples
Last reviewed 19 September 2026. How results are checked: How we verify.