Data Size Converter
This converter uses the binary (1024-base) convention: 1 KB = 1024 bytes, 1 MB = 1024 KB, and so on. That is what your operating system reports. Storage manufacturers use the decimal (1000-base) convention instead, which is exactly why a “1 TB” drive shows up as about 931 GB.
Binary vs decimal, and the 7% gap
Each step up the ladder, the two conventions drift apart by 2.4%. By terabytes the gap is about 10%: a drive sold as 1,000,000,000,000 bytes (1 decimal TB) is only 0.909 binary TB, which your computer labels “931 GB”. Nothing is missing – the two systems just count differently. The IEC names KiB, MiB and GiB were introduced to mean the binary sizes unambiguously, but KB/MB/GB in everyday software still usually mean binary.
Storage sizes in practice
| Size | Roughly holds |
|---|---|
| 1 MB | a high-quality photo, or a short document |
| 1 GB | about 250 songs, or 30 minutes of HD video |
| 1 TB | about 250,000 photos, or 40 hours of 4K video |
Bits vs bytes for connection speeds
One more trap: internet speeds are quoted in bits per second (Mbps), while file sizes are in bytes (MB). There are 8 bits to a byte, so a 100 Mbps connection downloads at about 12.5 MB/s at best. To estimate a download time from a file size and a speed, bring the time converter in for the seconds-to-minutes step.
FAQ
Why does my 1 TB drive show only 931 GB?
The manufacturer counts 1 TB as 1,000,000,000,000 bytes (decimal). Your OS counts in binary, where 1 TB is 1,099,511,627,776 bytes. The same number of bytes divided the binary way comes to about 0.909 TB, shown as 931 GB.
How many bytes are in a kilobyte?
1,024 in the binary convention (used by Windows and this tool); 1,000 in the decimal convention (used by storage makers). "KiB" always means 1,024.
How many MB in a GB?
1,024 MB in the binary convention. So a 4 GB file is 4,096 MB.
What is the difference between Mbps and MB/s?
Mbps is megabits per second (network speed); MB/s is megabytes per second (transfer rate). Divide Mbps by 8 to get MB/s - 80 Mbps is about 10 MB/s.