When you need this conversion
Checking whether files fit an upload limit, a USB stick or a data plan. Email attachments, app sizes and phone storage all mix megabytes and gigabytes, and a few hundred megabytes here and there add up.
Decimal and binary units
There are two systems:
- Decimal (SI): 1 kB = 1,000 bytes, 1 MB = 1,000,000 bytes, 1 GB = 1,000 MB. Used by storage makers, macOS, iOS, Android and network speeds.
- Binary (IEC): 1 KiB = 1,024 bytes, 1 MiB = 1,024 KiB, 1 GiB = 1,024 MiB. Used by Windows (which still writes MB and GB) and some Linux tools.
This converter uses decimal MB and GB. Switch the units to MiB and GiB to see binary values.
Useful values
- 500 MB = 0.5 GB
- 700 MB = 0.7 GB (a CD)
- 4,700 MB = 4.7 GB (a single-layer DVD)
- 25,000 MB = 25 GB (a Blu-ray disc)
Common mistakes
Dividing by 1,024 with decimal labels. 2,048 MB is 2.048 GB, not 2 GB. It’s 2 GiB only if the 2,048 was MiB.
Mixing bits and bytes. Internet speeds are in megabits (Mb). A 100 Mb file is only 12.5 MB.
For the reverse, use GB to MB. To see how Windows reports sizes, try GB to GiB.