MB to GB Converter
Enter a value in megabytes and get the result in gigabytes right away. Switch between the binary standard (1 GB = 1,024 MB), used by operating systems and RAM specs, and the SI decimal standard (1 GB = 1,000 MB), used by hard drive and storage device manufacturers. The reverse conversion from GB back to MB is built in: just change the direction toggle.
How many MB are in a GB?
The answer depends on which standard you use. In the binary system (used by operating systems, RAM, and firmware), 1 GB equals exactly 1,024 MB because a gigabyte is 2^30 bytes and a megabyte is 2^20 bytes - a ratio of 2^10 = 1,024. In the SI decimal system (used by hard drive and SSD manufacturers, and defined by the International System of Units), 1 GB equals exactly 1,000 MB because the prefix "giga" means 10^9 and "mega" means 10^6. The difference between the two results grows as the file size grows: at 1,000 MB the gap is 24 MB, but at 1,000,000 MB the gap is about 24,000 MB.
Binary vs SI decimal: why the two standards exist
Computer memory has always been built on powers of two, so early engineers used the nearest power of two to the metric prefix: 1,024 for "kilo", 1,048,576 for "mega", and so on. Storage manufacturers later adopted the simpler metric definitions (1,000, 1,000,000, etc.) to make their products appear larger - a 500 GB hard drive contains 500,000,000,000 bytes in SI terms, but Windows and macOS (which count in binary) report it as about 465 GB. To reduce confusion, the IEC introduced dedicated binary prefixes in 1998: kibibyte (KiB, 1,024 B), mebibyte (MiB, 1,048,576 B), gibibyte (GiB, 1,073,741,824 B), and so on. However, most everyday usage still mixes the two systems informally.
Converting MB to GB step by step
To convert megabytes to gigabytes, divide the number of megabytes by the conversion factor for your chosen standard. In binary: GB = MB / 1,024. In SI decimal: GB = MB / 1,000. For example, a 512 MB file is 512 / 1,024 = 0.5 GB in binary, or 512 / 1,000 = 0.512 GB in SI. To go the other direction (GB to MB), multiply instead of divide: 0.5 GB x 1,024 = 512 MB in binary, or 0.5 GB x 1,000 = 500 MB in SI.
Which standard should you use?
Use binary (1,024) when you are working with operating system reports, RAM specifications, virtual memory, or file system outputs - Windows Explorer, the macOS Finder (in recent versions), and most Linux tools all report storage in binary units even if they label them GB rather than GiB. Use SI decimal (1,000) when you are reading manufacturer specs for hard drives, SSDs, USB drives, SD cards, or optical media - the capacity printed on the packaging uses SI. If you are writing technical documentation or scientific work, the strictest approach is to use the IEC binary prefixes (MiB, GiB) for binary quantities and reserve MB/GB for SI decimal quantities only.
Common file sizes in MB and GB
| Item | Approx. size (MB) | Approx. size (GB) |
|---|---|---|
| Standard email (no attachment) | 0.075 MB | 0.000073 GB |
| MP3 audio (3 min, 128 kbps) | 3 MB | 0.003 GB |
| JPEG photo (smartphone, 12 MP) | 4 MB | 0.004 GB |
| RAW photo (DSLR) | 25 MB | 0.024 GB |
| HD video (1 min, 1080p) | 130 MB | 0.127 GB |
| Standard app (smartphone) | 200 MB | 0.195 GB |
| 4K video (1 min) | 375 MB | 0.366 GB |
| HD movie (2 hr, Blu-ray encode) | 10,240 MB | 10 GB |
| USB drive (typical) | 32,768 MB | 32 GB |
| SSD (entry level laptop) | 524,288 MB | 512 GB |
| Hard drive (desktop) | 1,048,576 MB | 1,024 GB |
Approximate sizes for everyday files and storage devices. Binary values shown (1 GB = 1,024 MB).
Frequently asked questions
Is 1 GB equal to 1,000 MB or 1,024 MB?
Both are in common use. The SI (International System of Units) definition says 1 GB = 1,000 MB because "giga" means 10^9 and "mega" means 10^6. The binary definition, used by operating systems and RAM, says 1 GB = 1,024 MB because computers work in powers of two. Hard drive manufacturers use the SI definition, so a "1,000 GB" drive appears as about 931 GB in Windows, which counts in binary.
Why does my hard drive show less space than advertised?
Hard drives are marketed using SI decimal units (1 GB = 1,000 MB), but Windows and most operating systems display storage using binary units (1 GB = 1,024 MB). A 1,000 GB drive contains 1,000,000 MB in SI terms, which is only 976.6 GB in binary - the roughly 2.4% gap is not missing space, just a difference in counting method. macOS switched to reporting in SI units in macOS 10.6 (Snow Leopard), so the same drive shows as 1 TB there.
How do I convert GB back to MB?
Multiply the number of gigabytes by the factor for your standard. In binary: MB = GB x 1,024. In SI: MB = GB x 1,000. So 2.5 GB is 2,560 MB in binary and 2,500 MB in SI. Use the "GB to MB" direction toggle in this calculator to do the reverse conversion automatically.
What is the difference between MB and MiB, and GB and GiB?
MB (megabyte) and GB (gigabyte) are ambiguous terms that can refer to either the binary or decimal value depending on context. MiB (mebibyte) and GiB (gibibyte) are IEC-defined binary prefixes that mean exactly 1,048,576 bytes and 1,073,741,824 bytes respectively - no ambiguity. Technical standards, Linux tools like "df -h --si", and engineering documents increasingly use the IEC prefixes for clarity, while everyday consumer language sticks with MB/GB for both meanings.
How many MB is 1 GB of mobile data?
Mobile carriers typically use the SI decimal standard, so 1 GB of mobile data is 1,000 MB. A 5 GB mobile plan is 5,000 MB. However, your phone may display data usage in binary units, which could cause a small discrepancy between what the carrier charges and what the phone reports.
How do I convert MB to TB?
In binary: TB = MB / (1,024 x 1,024) = MB / 1,048,576. In SI: TB = MB / (1,000 x 1,000) = MB / 1,000,000. For example, 500,000 MB is 500,000 / 1,048,576 = approximately 0.4768 TB in binary, or 500,000 / 1,000,000 = 0.5 TB in SI. This calculator shows the TB equivalent alongside the GB result.