File size converter — KB, MB, GB, KiB, MiB, GiB
Convert file sizes between decimal units (KB, MB, GB) and binary ones (KiB, MiB, GiB), and estimate how long a download takes at a given speed.
Runs entirely in your browser — nothing is uploaded.
Binary (1024-based)
Decimal (1000-based)
Storage makers use decimal units (1 GB = 1,000,000,000 bytes) while operating systems mostly report binary (1 GiB = 1,073,741,824). That is why a "1 TB" drive shows as about 931 GB. Download times ignore protocol overhead, so expect real transfers to be 10–20% slower.
How to use
- Enter a size and unit. Binary and decimal units are grouped separately.
- Read both scales. Every unit is shown at once, so you can see the gap between them.
- Set a connection speed. To estimate download time.
Questions
Why does my 1 TB drive show as 931 GB?
Because the manufacturer counts 1 TB as 1,000,000,000,000 bytes, while your operating system divides by 1,024 three times and calls the result GB. The drive holds exactly what was advertised — the two are just using different definitions.
What is the difference between MB and MiB?
MB is 1,000,000 bytes; MiB is 1,048,576. The binary units (KiB, MiB, GiB) were standardised in 1998 precisely to end this ambiguity, though usage is still inconsistent.
Why is my download slower than the calculation?
Because the estimate is pure arithmetic on your line speed. Real transfers lose 10–20% to protocol overhead, and are further limited by the server, congestion and Wi-Fi. Also note speeds are quoted in megabits, not megabytes — divide by 8.
How many bits are in a byte?
Eight. Connection speeds are advertised in bits per second and file sizes in bytes, which is why a 100 Mbps line downloads at roughly 12.5 MB/s at best.