Data Storage Converter (GB to MB)
Convert gigabytes to megabytes using the decimal (SI) convention, where one gigabyte is 1000 megabytes. Enter a size in GB and the tool returns MB. It is the conversion you need for data-plan allowances, file and download sizes, and storage labels — most of which are quoted in decimal units even though some software counts in binary.
Calculate
Default result: 1,000 MB
Data Storage Converter (GB to MB) · Result
calculators.dev
Megabytes
1 gb
Reviewed by the calculators.dev team · Last updated 2026-06-23
How to calculate
Type the size in gigabytes and read the megabytes below. To convert by hand under the decimal convention, multiply gigabytes by 1000: a 0.5 GB file is 500 MB. To convert megabytes back to gigabytes, divide by 1000. If your operating system reports binary sizes, see the assumptions below for the 1024 difference.
megabytes = gigabytes × 1000 (decimal / SI, IEC 80000-13), where 1 kB = 1000 B, 1 MB = 1000 kB, and 1 GB = 1000 MB. Equivalently, gigabytes = megabytes ÷ 1000. The binary convention instead uses powers of 1024 and the names KiB, MiB, GiB.
Example calculation
1 gigabyte multiplied by 1000 megabytes per gigabyte is 1000 megabytes, using the decimal (SI) convention. In the binary convention used by some operating systems, 1 GiB equals 1024 MiB instead — see the assumptions for which applies to you.
- result
- 1,000 MB
Assumptions
- This page uses the DECIMAL (SI) convention: 1 GB = 1000 MB, 1 MB = 1000 kB (IEC 80000-13). It is what storage makers, data plans, and most file sizes use.
- Some operating systems (notably older Windows) count in BINARY: 1 GiB = 1024 MiB. That is why a '1 TB' drive can show as about 931 'GB' in those tools — same bytes, different counting base.
- If you need the binary value, multiply by 1024 instead of 1000 per step; the proper binary unit names are KiB, MiB, GiB.
Common mistakes
- Mixing decimal and binary — comparing a decimal-labeled drive to a binary file-manager reading makes the drive look smaller than advertised when no bytes are missing.
- Assuming 1 GB is always 1024 MB; under the SI convention used here it is 1000 MB.
- Reversing the direction — multiply by 1000 for megabytes, divide by 1000 for gigabytes.
Frequently asked questions
How many MB is 1 GB?
Under the decimal (SI) convention used here, 1 GB is 1000 MB. Under the binary convention, 1 GiB is 1024 MiB.
Why does my drive show less space than the label?
Storage is labeled in decimal units (1 GB = 1000 MB), but some operating systems count in binary (1 GiB = 1024 MiB). No space is missing — the two systems just count differently.
What is the difference between GB and GiB?
GB is decimal (1000-based) and GiB is binary (1024-based). A GiB is about 7.4% larger than a GB.
Which convention should I use?
For data plans, downloads, and storage labels, use decimal (this tool). Use binary only when your software explicitly reports KiB, MiB, or GiB.