Storage Unit Converter
Convert between TB and TiB, GB and GiB, and see why they differ.
What you provide
Result
1 TB = 0.909495 TiB
Decimal units step by 1,000 and binary units by 1,024, and the gap compounds with each step: about 2.4% at kilobytes, 7% at gigabytes and just under 10% at terabytes. Drive makers, network gear and cloud billing use the decimal meaning. Windows and most file managers compute the binary value and label it with the decimal name, which is where the missing capacity people report actually comes from. macOS and most Linux tools report decimal, which is why the same disk looks larger there.
- Result
- 0.909495 TiB
- The other definitionDecimal, as drive makers and cloud invoices label it
- 1 TB
- In bytes
- 1,000,000,000,000
- Difference at this sizeBetween the decimal and binary readings
- 9.1%
What this cannot tell you
- Unit arithmetic on the number you type. It does not read any drive and cannot tell you how much space you have.
- It converts storage units only. Network speeds are quoted in bits per second rather than bytes, so dividing by eight comes first if you are converting a transfer rate.
Take this with you
How this calculation works
Two different meanings of the same prefixes are in everyday use. Decimal units step by 1,000, so a terabyte is 1,000,000,000,000 bytes. Binary units step by 1,024, so a tebibyte is 1,099,511,627,776 bytes. The converter works through raw bytes, then shows the answer in both families side by side, because the practical question is almost always why one number differs from another rather than what a single conversion produces.
What the results mean
- The other definition
- The same quantity expressed in the opposite family. This is normally the line people came for, since it explains the discrepancy between the box and the operating system.
- In bytes
- The unambiguous figure. When two systems disagree about a size, comparing bytes settles it.
- Difference at this size
- How far apart the two readings are. It grows with each prefix step, from about 2.4% at kilobytes to just under 10% at terabytes.
Common problems and fixes
- My 1 TB drive shows as 931 GB
- Nothing is missing. The drive holds a genuine 1,000,000,000,000 bytes, which is a terabyte by the standard meaning of the prefix. Windows then divides by 1,024 three times and labels the result GB, when the number it computed is gibibytes. The same drive reports as about 1 TB on macOS and most Linux tools, which use decimal units throughout.
- A backup that fits on paper will not fit on the disk
- Check whether the two figures use the same family before assuming the arithmetic is wrong, because a 10% gap at terabyte scale is easily enough to overflow a disk. Then leave real headroom on top. Filesystems reserve space, snapshots consume it invisibly, and most filesystems slow noticeably once they pass about 85% full.
Frequently asked questions
Why do drive makers use decimal units?
Because the prefixes are SI units that mean powers of a thousand everywhere else in engineering, and because a drive is a linear array of sectors with no natural power-of-two size. Computing borrowed the same prefixes for powers of two early on, which was convenient and ambiguous, and the IEC introduced kibi, mebi and gibi in 1998 to separate them. Storage vendors adopted the standard meaning; most operating systems did not adopt the standard labels.
Is 1 GB the same as 1 GiB?
No. A gigabyte is 1,000,000,000 bytes and a gibibyte is 1,073,741,824, about 7.4% more. They are frequently used interchangeably in software, which is why RAM, which really is sold in binary sizes, is labelled in GB while meaning GiB.
How do I convert a file size into a download time?
Convert the file to bits by multiplying bytes by eight, then divide by the connection speed in bits per second. A 1 GB file over a 100 Mbps line is 8,000 megabits divided by 100, so 80 seconds at the theoretical maximum and more like 95 to 110 seconds in practice.
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