Human readable file size converter

Convert between bytes, kB, MB, GB and KiB, MiB, GiB — and see both at once, which is the answer to why a 1 TB drive shows as 931 GB.

1 · A size

Size

Read an ambiguous unit as

KiB, MiB and GiB are always binary whichever you pick. This only changes what kB, MB and GB mean.

0Bytes exactly

0Decimal

0Binary

Decimal (SI)

The size in decimal units
Unit	Value

Binary (IEC)

The size in binary units
Unit	Value

How long would it take to transfer?

Connection speed in megabits per second

Internet speeds are sold in bits, not bytes. An 8 Mbit line moves one megabyte per second, not eight.

Windows reports in binary but labels it "MB", which is where the missing gigabytes go: a 1 TB drive holds exactly 1,000,000,000,000 bytes and Windows divides by 1024 four times to show 931. Nothing is faulty. macOS and Linux report decimal.

Why 1 MB is two different numbers

This is the whole reason the tool exists. 1 MB is 1,000,000 bytes in the decimal convention, and 1 MiB is 1,048,576 bytes in the binary one. Both are correct; they are different units.

The confusion is that Windows reports in binary but labels it "MB". So your 1 TB drive — 1,000,000,000,000 bytes, exactly as sold — is divided by 1024 four times and displayed as "931 GB". Nothing is missing and nothing is faulty. macOS and Linux report decimal and show the full number.

Both at once

Rather than picking one convention and being quietly wrong half the time, this shows every unit in both tables from one exact byte count. An explicitly binary unit such as MiB is always binary; an ambiguous one such as MB is read according to the mode you choose.

Transfer time, and the other factor of eight

Internet speeds are sold in bits per second, not bytes. An 8 megabit connection moves one megabyte per second, not eight. Enter a speed and the tool works out how long a file actually takes.

Example

1 TB is exactly 1,000,000,000,000 bytes, which is 931.32 GiB. A 700 MB file over a 20 Mbit/s line takes about four minutes and forty seconds.

Limitations

Sizes above roughly 9 petabytes are refused rather than answered. Beyond that a browser cannot hold consecutive whole numbers exactly, and a rounded byte count presented as exact would be worse than no answer.