About the Data Size Converter
Two unit systems are in use. Decimal SI prefixes multiply by 1000: 1 kB = 1,000 bytes, 1 MB = 1,000,000 bytes, 1 GB = 109 bytes. Binary IEC prefixes multiply by 1024: 1 KiB = 1,024 bytes, 1 MiB = 1,048,576 bytes, 1 GiB = 1,073,741,824 bytes. Drive makers, network speeds and macOS (since 10.6) use decimal; Windows Explorer, RAM sizes and many Linux tools use binary but often label them “KB/MB/GB”. The difference grows with each step: about 2.4% at kilo, 7.4% at giga and 12.6% at peta.
That is why a “1 TB” drive shows up as about 931 GB in Windows: 1012 bytes ÷ 10243 ≈ 931.32 GiB. The table puts both systems side by side so you can see exactly which one a number came from. Bits (lower-case b) are one eighth of a byte (upper-case B); network links are quoted in bits per second, so a 100 Mbit/s connection moves at most 12.5 MB/s.
The transfer-time estimate divides the size by the bandwidth you enter, and the link table repeats it for common connections — mobile data, home broadband, USB 2.0, Gigabit Ethernet, USB 3.0 and 10 GbE. These are ideal figures at full line rate; protocol overhead, disk speed and latency usually make a real copy 5–15% slower, and much slower for many small files.
How to use it
- Enter a size and choose its unit (B, kB … PB, KiB … PiB, or bits).
- Read the value in every SI and IEC unit in the side-by-side table.
- Enter a bandwidth and unit to estimate the transfer time.
- Copy any value with the button next to it.