Convert Data Sizes Between Units
Enter a size in any unit to see it in decimal (MB, GB), binary (MiB, GiB) and bit units side by side. A transfer-time estimate and a drive-capacity explainer help with real-world questions.
How to convert file sizes
- Type a value and choose its unit in the From list.
- Choose the unit you want in the To list, or use the swap button — the full table below shows every other unit too.
- Enter your connection speed in Mbps (or pick a preset) to estimate how long the transfer takes.
KB or KiB? Two ways to count
In the SI system a kilobyte is 1,000 bytes, so 1 GB is 1,000,000,000 bytes. Computers address memory in powers of two, so the IEC defined the kibibyte (KiB, 1,024 bytes), mebibyte (MiB) and gibibyte (GiB). Drive makers and macOS use decimal units; Windows uses binary units but labels them KB, MB and GB, which is why a 1 TB disk appears as about 931 GB. Network speeds are quoted in bits, so a 100 Mbps line moves at most 12.5 MB per second. To check the exact byte count of a real file, open it in the File Information Viewer.
Benefits
- Shows decimal, binary and bit units together, so there is no guessing which "GB" someone meant.
- Explains the advertised-versus-displayed capacity gap with your own numbers.
- Transfer estimates include a realistic 80% efficiency figure alongside the theoretical best case.
Limitations
- Byte counts above 2⁵³ (about 9 PB) cannot be represented exactly in JavaScript numbers, so the last digits are rounded.
- Transfer times are estimates; real speeds depend on Wi-Fi quality, protocol overhead and the remote server.
Privacy and security
This converter only does arithmetic on the numbers you type. No files are read and nothing is sent anywhere.
Read our privacy policy for details about the site as a whole.
Frequently asked questions
Is 1 GB 1,000 MB or 1,024 MB?
Strictly, 1 GB is 1,000 MB and 1 GiB is 1,024 MiB. In everyday use — especially in Windows and for RAM — "GB" often means GiB, so check which convention your software uses.
How many megabytes per second is 100 Mbps?
Divide by eight: 100 megabits per second is 12.5 megabytes per second at best. In practice expect around 10–11 MB/s after overhead.
Why are bits written with a lowercase b?
By convention b means bit and B means byte. Mbps (or Mb/s) is megabits per second, while MB/s is megabytes per second — eight times larger.