Byte Size Converter
Convert data sizes between every unit, showing both the powers-of-ten and powers-of-two readings.
About this tool
Converts data sizes and shows both interpretations of every unit, because "KB" means two different things depending on who wrote it.
Storage manufacturers use **powers of ten**: a kilobyte is 1,000 bytes, and a 1TB drive holds 10^12 of them. Operating systems mostly use **powers of two**: a kibibyte is 1,024 bytes, and that same drive reports as 931GB. Neither is wrong, and the gap is 2.4% at gigabyte scale and nearly 10% at terabyte scale — enough to matter and small enough to go unnoticed.
Transfer time is included because it is usually the question behind a file size, and it makes the difference between a **megabit** and a **megabyte** visible. Connection speeds are quoted in bits and file sizes in bytes, and the factor of eight between them is dropped constantly.
Common questions
Why does my 1TB drive show as 931GB?
The manufacturer counted in powers of ten — 10^12 bytes. The operating system divides by 1,024 three times and gets 931. The drive holds exactly what was advertised; the two are using different units with the same name.
What is the difference between MB and MiB?
MB is 1,000,000 bytes and MiB is 1,048,576. The binary units — KiB, MiB, GiB — were standardised specifically to remove this ambiguity, and are still used less often than the ambiguous ones.
Why is my download slower than my connection speed?
Partly the bits-versus-bytes factor of eight: a 100 Mbps connection tops out around 12.5 MB/s. The rest is protocol overhead, latency and whatever the other end can send, so real throughput of 70 to 90 per cent of the theoretical figure is normal.
Which should I use when writing about file sizes?
Powers of ten with the plain units, which is what most readers assume and what storage is sold in. Use the binary units explicitly when you mean them, and never write KB while meaning 1,024 bytes.