How to Convert MB to GB (and Why It Is Confusing)

To convert megabytes to gigabytes, divide by 1,000 in decimal units, the system drive makers and networks use. So 1,500 MB is 1.5 GB. The data storage converter shows both the decimal and the binary answer, which is where this gets interesting.

That is the simple version. The reason MB and GB cause so much confusion is that there are two systems, not one.

Two systems: decimal and binary

Digital storage can be counted two ways:

Decimal (SI): a kilobyte is 1,000 bytes, a megabyte is 1,000 kilobytes, a gigabyte is 1,000 megabytes. This is what storage manufacturers, network speeds and most marketing use.
Binary: a kibibyte is 1,024 bytes, a mebibyte is 1,024 kibibytes, a gibibyte is 1,024 mebibytes. This matches how computers address memory, and some operating systems use it while still labelling it “MB” and “GB”.

So 1 GB is either 1,000 MB or 1,024 MB depending on which system you mean. Both are correct; they just answer slightly different questions.

How to convert MB to GB

Decimal (the common case)

Divide MB by 1,000.

500 MB → 0.5 GB
2,500 MB → 2.5 GB

Binary

Divide MB by 1,024.

1,024 MB → 1 GB (gibibyte)
4,096 MB → 4 GB

The data storage converter shows decimal KB/MB/GB/TB and binary KiB/MiB/GiB/TiB side by side, so you can see the gap.

Why your drive looks smaller than the box

This is the classic source of confusion. A “1 TB” drive holds 1,000,000,000,000 bytes, the decimal terabyte the maker advertises. But many operating systems display that in binary, where a terabyte is 1,099,511,627,776 bytes. Divide the real capacity by the larger binary unit and it reports as about 931 GB. Nothing is missing; the drive is full size, and your computer is just measuring with a bigger ruler.

When it matters

For most people, the decimal answer (divide by 1,000) is the one they want, since it matches how storage and data plans are sold. The binary distinction matters when you are checking why reported sizes differ, working close to a capacity limit, or doing technical work where the exact byte count counts.

To see how binary numbers themselves work, see the number base converter.

Frequently asked questions

How many MB are in a GB?

It depends on the system. In decimal units, used by drive makers and networks, 1 GB is 1,000 MB. In binary units, used by some operating systems, 1 GB (properly a gibibyte) is 1,024 MB. The difference is why advertised and reported sizes disagree.

Why does my hard drive show less space than the box says?

Drive makers count a gigabyte as 1,000,000,000 bytes (decimal), but your operating system often counts it in binary, where a gigabyte is 1,073,741,824 bytes. The drive is the advertised size; the computer is just measuring it differently, which makes the number look about 7 percent smaller.

What is the difference between MB and MiB?

A megabyte (MB) is 1,000,000 bytes in the decimal system. A mebibyte (MiB) is 1,048,576 bytes, the binary equivalent. They are close but not equal, and the gap grows at larger sizes.