File size converter.
Convert between bytes, kilobytes, megabytes, gigabytes, terabytes. Binary and decimal.
Converter
- B1000000000
- KB1000000
- MB1000
- GB1
- TB0.001
Why your hard drive shows less than advertised
Drive manufacturers count storage in decimal. A 1 TB drive is 1,000,000,000,000 bytes on the label. Your operating system counts in binary and divides by 1,024 three times to print the same number as a GB count, which lands at 931 GB. No bytes were lost. The label and the file manager just disagree on which power they divide by.
The IEC fixed the ambiguity in 1998 by introducing KiB, MiB, GiB, TiB for the binary versions. Most operating systems and most software ignored the new units and kept the old labels. The numbers below show both definitions side by side.
Quick reference
| Unit | Decimal (1000) | Binary (1024) |
|---|---|---|
| 1 KB / 1 KiB | 1,000 B | 1,024 B |
| 1 MB / 1 MiB | 1,000,000 B | 1,048,576 B |
| 1 GB / 1 GiB | 1,000,000,000 B | 1,073,741,824 B |
| 1 TB / 1 TiB | 1,000,000,000,000 B | 1,099,511,627,776 B |
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Send a fileFAQ
Why is 1 KB sometimes 1000 bytes and sometimes 1024?
Two competing definitions. The SI standard says 1 KB is 1,000 bytes. The older computing convention says 1 KB is 1,024 bytes because memory chips come in powers of two. The IEC introduced KiB, MiB, GiB to mean exactly the 1,024-based versions, but most operating systems still print KB and mean 1,024. This converter lets you switch between the two and see both numbers at once.
What unit do email providers use?
Almost always decimal. When Gmail says 25 MB, it means 25,000,000 bytes, not 26,214,400 bytes. Most messaging apps follow suit. When in doubt, plan for the smaller number. Your file does not get bigger on the wire, but the encoding overhead can push it past the cap.
Why does my 1 TB drive show as 931 GB?
Hard drive manufacturers use the decimal definition. 1 TB on the box is 1,000,000,000,000 bytes. The operating system divides that by 1,024 three times to print GB, which gives 931.32. No bytes are missing, the two numbers just count differently. SSD makers do the same thing.
Which is the right system to use?
Use whichever the surface uses. Storage marketing, ISP speeds, and most modern web standards use decimal. Operating systems, file managers, and download progress bars often use binary, but call it KB or GB. The number is the same byte count either way, only the label changes.
How precise is this converter?
Exact. JavaScript can hold integer byte counts up to 9 quadrillion without losing precision, which covers anything you can put on a disk. The displayed numbers are rounded to four significant figures for readability, the underlying calculation is not.
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