Megabytes to Gigabytes Converter

1 MB is the decimal SI megabyte equal to exactly 1,000,000 bytes (1,000 KB). 1 MiB is the binary IEC mebibyte equal to exactly 1,048,576 bytes (1,024 KiB, or 2^20). The same gap repeats at every scale: 1 GB = 1,000,000,000 bytes while 1 GiB = 1,073,741,824 bytes (about 7.4 percent larger). The difference comes from base 1,000 versus base 1,024, and it compounds with each step. By the time you reach terabytes, 1 TiB is about 10 percent larger than 1 TB.

Two reasons. First, the decimal definitions match the SI prefixes used everywhere else in science and engineering: 1 km = 1,000 m, 1 kg = 1,000 g, so 1 KB = 1,000 B is the consistent reading. Second, decimal numbers are bigger on the label, which is a marketing benefit at no extra manufacturing cost: a drive sold as 1 TB holds 1,000,000,000,000 bytes, but the same physical drive reported in binary GiB shows as only 931.32 GiB. The convention has been fixed by US courts (the 2007 Cho v. Seagate settlement formalized that 1 GB on a drive label means 1,000,000,000 bytes) and is now standard across every storage vendor.

The International Electrotechnical Commission published IEC 60027-2 in 1998, which defined the new binary prefixes kibi (Ki), mebi (Mi), gibi (Gi), tebi (Ti), and pebi (Pi). The names combine the SI prefix with bi (for binary), and they exist to remove ambiguity from the older convention where KB sometimes meant 1,000 bytes and sometimes 1,024 bytes. The IEEE adopted the same standard in 2005 (IEEE 1541), and IEC ratified the extension up to yobi (Yi, 2^80) in 2019. Linux, macOS Big Sur and later, and most modern documentation use the IEC names correctly; Windows still labels binary values with the decimal KB/MB/GB symbols.

Windows reports file and drive sizes in binary (powers of 1,024) but labels the values with decimal symbols (KB, MB, GB) instead of the correct IEC binary symbols (KiB, MiB, GiB). A 1 TB drive contains exactly 1,000,000,000,000 bytes per the SI/JEDEC label, which is 931.32 GiB in actual binary measurement. Windows displays that as 931 GB, which is mathematically wrong by name but matches the binary count on disk. macOS switched to the SI definitions in Snow Leopard (2009), so the same 1 TB drive shows as 1 TB on a Mac and 931 GB on a Windows machine, even though both report the same byte count under the hood.

Memory specs are almost always binary because RAM and CPU caches are built on power-of-two address lines: a 16 GB DIMM holds exactly 16 GiB (17,179,869,184 bytes), even though it is labeled GB. Same for SSD and HDD cache buffers, GPU memory, and L1/L2/L3 caches. Bandwidth specs are decimal: a 1 Gbps Ethernet link transfers 1,000,000,000 bits per second, a 100 Mbps connection is 100,000,000 bits per second, and cellular speed claims follow the same convention. Storage capacity is decimal on the label, binary on the operating system. The mixed practice is the source of most data-unit confusion, which is why the IEC binary prefixes exist.