What this calculator does
Converting megabytes to gigabytes looks like simple division, but the answer depends on which convention is being used. Storage manufacturers and most everyday marketing use the decimal convention, where 1 gigabyte is 1,000 megabytes. Some operating systems and file browsers instead use the binary convention, where 1 gigabyte is 1,024 megabytes, because computers naturally work in powers of two.
The gap between the two grows with the size of the number involved. At small amounts the difference barely matters, but a claimed 500 GB drive reports as roughly 465 GB in a binary-counting file manager, which is the most common reason people think storage has "gone missing" when nothing actually has.
The formula
Divide the megabyte figure by 1,000 to get gigabytes under the decimal convention, or by 1,024 under the binary convention, and the reverse (multiply) to go from gigabytes back to megabytes. Pick the convention that matches whatever number you are trying to check: decimal for a manufacturer’s advertised capacity, binary for a figure reported by an operating system.
| Term | Meaning |
|---|---|
| Decimal (SI) | Treats 1 GB as exactly 1,000 MB, following the metric prefix system used in most advertising and specifications. |
| Binary (IEC) | Treats 1 GB as exactly 1,024 MB (2¹⁰), matching how many operating systems and file managers report storage. |
| MB | Megabyte, the amount being converted from or to. |
The inputs explained
| Field | What to enter |
|---|---|
| Convert | Choose whether you are converting megabytes into gigabytes, or gigabytes back into megabytes. |
| Convention | Choose the counting convention that matches the figure you already have. |
| Amount | The amount, in the unit you are converting from, to convert. |
When to use it
Checking a downloaded file size
A download manager or website might list a file in MB while you are budgeting storage in GB; converting puts both figures in the same unit.
Explaining a storage discrepancy
A drive advertised at a round number of gigabytes (decimal) always shows a smaller number in an operating system that reports storage in binary gigabytes; converting the advertised figure to binary shows exactly why.
Sizing a data plan or backup
Cloud storage and phone plans are usually sold in decimal gigabytes, so converting megabyte-sized files or backups into that same convention avoids under- or over-estimating how much of a plan they will use.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How many gigabytes is a given number of megabytes?
A range of common megabyte amounts, converted to decimal gigabytes.
| Megabytes | Result |
|---|---|
| 500 MB | 0.5000 GB |
| 1,000 MB | 1.000 GB |
| 2,500 MB | 2.500 GB |
| 5,000 MB | 5.000 GB |
| 10,000 MB | 10.000 GB |
| 500,000 MB | 500.000 GB |
How the decimal and binary conventions diverge at scale
The same megabyte amount, converted under each convention, showing how far apart they drift.
| Convention | Result |
|---|---|
| Decimal (1,000) | 500.000 GB |
| Binary (1,024) | 488.281 GB |
Questions
Why do file sizes look smaller in Windows or macOS than the box says?
Most operating systems report storage using the binary convention (1 GB = 1,024 MB = 1,024³ bytes), while manufacturers advertise capacity using the decimal convention (1 GB = 1,000 MB = 1,000³ bytes). Nothing is missing; the two are just counting differently.
Which convention should I use?
Match whichever figure you are trying to verify or compare against: decimal for advertised storage capacity or data plans, binary for a size reported by a file manager or operating system.
Is a megabyte the same as a megabit?
No. A megabyte (MB) is 8 megabits (Mb). Storage is measured in bytes; network and internet connection speeds are usually measured in bits per second, which is a different unit entirely.
Does the difference matter for small files?
Barely. At a few megabytes the decimal and binary results are within a fraction of a percent of each other. The gap only becomes noticeable, and eventually significant, once amounts reach into the hundreds of gigabytes or terabytes.
For converting a download speed in megabits per second into the gigabytes it delivers over time, see the Mbps to GB calculator. For smaller amounts, the kilobytes to megabytes calculator covers the step below.