File Size Converter
Parse a human size like 1.5MB, 500 KiB or 1e6 and see it in every other unit, with the binary and decimal readings both shown. MB and MiB are different units with different numbers, and the difference is 2.4% by the time you reach the gibibyte — Furtu surfaces that rather than picking one for you.
Auto assumes the SI meaning, which is what the prefix means, and tells you what the binary reading would be.
How file size converter works
- Type a sizeA number with or without a unit: 1.5MB, 500 KiB, 2 GB, 1e6.
- Choose how to read an ambiguous unitOr let Furtu read it as decimal and warn about the binary alternative.
- Read every unitBits and bytes, decimal and binary, all at once.
What you get
Convert between bytes, kilobytes, mebibytes and bits, without guessing MB. Everything happens inside this page: the file is read by your browser, transformed in memory and handed straight back to you as a download. There is no upload queue, no waiting for a server, and nothing left behind when you close the tab.
Supported formats
This tool works on text you paste or type, so there is no file format to worry about. Nothing you type is sent anywhere.
Limitations, stated up front
- Bits are shown as a value, not a transfer rate. Sustained throughput depends on protocol overhead and is never the full line rate.
- Ambiguous single-letter units such as K or M are assumed decimal, which is a guess that is flagged in the notes.
Frequently asked questions
Is MB the same as MiB?
No. MB is decimal: 1 MB is 1,000,000 bytes, as the SI prefixes require. MiB is binary: 1 MiB is 1,048,576 bytes, which is 1,024 KiB of 1,024 bytes. The gap is small for megabytes and large for gigabytes — a 1 TB drive is 1,099,511,627,776 bytes, and dividing that by a million gives 1,099 GB, not 1,000. That gap is why a drive never looks as big as it was advertised.
What does 100 Mbps mean in MB?
Bits, not bytes: 100 megabits per second is 12.5 megabytes per second, because a byte is eight bits. A connection advertised in megabits per second is therefore a different number of bytes per second from the one suggested, and a 100 Mbps line moves a 1 GB file in about 80 seconds at the full rate.
What happens to 1e6?
It is read as a number with no unit. Furtu treats it as bytes and says so, and 1e6 bytes is 1 MB decimal or 976.5625 KiB binary. Scientific notation is useful for a byte count from a script and uselessly ambiguous without a unit, so Furtu never supplies one silently.
Why does a 256 GB drive show as 238 GB?
Because the label is decimal and the operating system reports binary. 256,000,000,000 bytes is 238.4 GiB. It is a labelling convention, not a missing chunk of storage, and this converter shows both numbers side by side so the arithmetic is visible.
Is anything uploaded when I convert a size?
No. It is arithmetic on a number you typed, done in your browser. Furtu does not read a file's size from your disk, because the tool never asks for a file.