MB to GB Converter

Convert a storage size between megabytes and gigabytes in either direction.

Supports the base-10 (SI) 1 GB = 1,000 MB and base-2 1 GB = 1,024 MB definitions.

Updated August 13, 2026

CreatorFrank Zhao

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Introduction / overview

The MB to GB Converter switches a storage size between megabytes (MB) and gigabytes (GB) in either direction. It is built around a small but crucial detail: a gigabyte can mean 1,000 megabytes or 1,024 megabytes, depending on which convention your device follows. The calculator supports both, so you can match the number on a drive label, a cloud-storage plan, a file manager, or a memory spec sheet.

Type a size into either field and the other updates automatically. Pick the numeral system first, then the conversion follows — you never divide by 1,000 or 1,024 by hand.

It is the tool to reach for when you are sizing files and folders, comparing storage devices, checking how much an app or backup really takes, or trying to understand why a freshly formatted drive seems smaller than the box says.

How to use / quick start

Pick the numeral system that matches your device

Choose base-10 (SI) for hard drives, SSDs, cloud storage and network specs, which quote $1\ \mathrm{GB} = 1000\ \mathrm{MB}$ . Choose base-2 (binary) for memory and software that counts in $1024$ , where $1\ \mathrm{GB} = 1024\ \mathrm{MB}$ .

Enter the size you know

Type it into Megabytes or Gigabytes — either field works, and comma-grouped input such as 1,500 is accepted.

Read the equivalent in the other field

The conversion happens automatically, so the same size appears in both units at once. Re-enter from the other side whenever you need the reverse.

Example — convert a 2 GB folder to megabytes

Select base-10 (SI) and enter $2$ in Gigabytes. Because a decimal gigabyte holds exactly 1,000 megabytes:

2\ \mathrm{GB}

=

2 \times 1000

=

2000\ \mathrm{MB}

Under base-2 (binary) the same input reads as 2,048 MB — the difference matters when you compare a vendor label against what a binary-counting program reports.

Calculation method

One relationship covers both directions. A gigabyte is a fixed multiple of a megabyte, and that multiple is the only thing the numeral system changes:

\mathrm{MB} = \mathrm{GB} \times b, \qquad b = 1000\ \text{(base-10)} \ \text{or}\ 1024\ \text{(base-2)}

In the base-10 (SI) convention the multiplier is exactly $1000$ :

\mathrm{MB} = \mathrm{GB} \times 1000

\ \ ,\ \

\mathrm{GB} = \frac{\mathrm{MB}}{1000}

In the base-2 (binary) convention the multiplier is $1024$ , since $1024 = 2^{10}$ :

\mathrm{MB} = \mathrm{GB} \times 1024

\ \ ,\ \

\mathrm{GB} = \frac{\mathrm{MB}}{1024}

Variables

$\mathrm{MB}$ — the size in megabytes
$\mathrm{GB}$ — the size in gigabytes
$b$ — the numeral system multiplier (1,000 or 1,024)

Either field is a valid starting point. Enter a value in megabytes and the gigabytes re-derive, or start from gigabytes and read the megabytes — the conversion runs just as cleanly in both directions. Because the factors are exact integers, the math never introduces rounding on its own.

Base-10 vs. base-2: why there are two gigabytes

The two definitions come from two different ways of counting. The SI prefixes used in the metric system are powers of ten — $\mathrm{kilo} = 10^3$ , $\mathrm{mega} = 10^6$ , $\mathrm{giga} = 10^9$ — so a decimal gigabyte is $10^9 = 1{,}000{,}000{,}000$ bytes. Computers, however, organize data in powers of two, and $2^{10} = 1024$ is very close to 1,000. Early software borrowed the “kilo” name for 1,024, and the habit spread to megabytes and gigabytes.

The IEC binary units (MiB, GiB)

To end the confusion, the International Electrotechnical Commission (IEC) standardized binary prefixes in 1998: kibi (Ki), mebi (Mi), and gibi (Gi), each meaning a power of 1,024. The relationships are exact:

1\ \mathrm{MiB} = 2^{20}\ \mathrm{B} = 1{,}048{,}576\ \mathrm{B}

\ \ ,\ \

1\ \mathrm{GiB} = 2^{30}\ \mathrm{B} = 1{,}073{,}741{,}824\ \mathrm{B}

By contrast, $1\ \mathrm{MB} = 10^6\ \mathrm{B}$ and $1\ \mathrm{GB} = 10^9\ \mathrm{B}$ in the decimal system. Storage device manufacturers quote the decimal figures, while memory makers and much software use the binary figures — exactly the split the NIST reference describes alongside the IEC table in its reference on binary prefixes.

This is why a “500 GB” drive so often shows less capacity than its label. The label uses decimal gigabytes; the operating system reports the same bytes in binary gigabytes:

500\ \mathrm{GB} = 500 \times 10^9\ \mathrm{B}

=

\frac{500{,}000{,}000{,}000}{2^{30}}

\approx

465.66\ \mathrm{GiB}

Neither number is wrong — they just use different units. Use base-10 (SI) when you are reading a vendor label, a cloud-storage tier, or a network spec, and base-2 (binary) when you want your result to match what Windows and many utilities display.

Real-world examples

Size a video project folder

Your edited video project is 4 GB and you want to know how much space it takes in megabytes. Under base-10 (SI), the answer is clean:

4\ \mathrm{GB}

=

4 \times 1000

=

4000\ \mathrm{MB}

If your editing or file-manager software counts in binary, expect 4,096 MB instead ( $4 \times 1024$ ). Checking both keeps your storage math consistent with the tool that actually reports the number.

Move 1,500 MB of photos onto a device

A folder of photos reads 1,500 MB and you want the figure in gigabytes. In base-10 (SI):

\frac{1500\ \mathrm{MB}}{1000}

=

1.5\ \mathrm{GB}

In base-2 (binary) the same folder is just under 1.5 GB — about $1.46\ \mathrm{GB}$ (1500 / 1024). The difference rarely matters for a quick capacity check, but it is exactly the kind of mismatch that shows up when a phone or console reports storage.

Frequently asked questions

Why is 1 GB equal to 1,000 MB sometimes and 1,024 MB other times?

Because there are two conventions. Base-10 (SI) follows the metric system, where $1\ \mathrm{GB} = 10^9$ bytes $= 1000\ \mathrm{MB}$ . Base-2 (binary) follows the powers of two that computers use, where $1\ \mathrm{GB} = 2^{30}$ bytes $= 1024\ \mathrm{MB}$ . Drive and cloud vendors quote the decimal number; much software and memory report the binary one. Pick the variant that matches your source.

What is the difference between GB and GiB (or MB and MiB)?

$\mathrm{GiB}$ (gibibyte) is the IEC's unambiguous name for a binary gigabyte: $2^{30} = 1{,}073{,}741{,}824$ bytes. $\mathrm{GB}$ stays reserved for the decimal $10^9$ bytes, and $\mathrm{MiB}$ plays the same role for megabytes ( $2^{20}$ bytes). This calculator uses the familiar MB/GB labels for both conventions, so just set the variant to match the system you are comparing against. If you are converting across the full range — kilobytes, terabytes, bits, or the binary KiB/MiB/GiB family — the byte converter covers every one of those units in a single place.

Which numeral system should I choose?

Match it to where your number comes from. Choose base-10 (SI) for hard-drive and SSD labels, cloud-storage tiers, and network speeds. Choose base-2 (binary) when you want the result to line up with what Windows, many file managers, and memory (RAM) reports. When in doubt, test a round number: if the tool shows a size that matches your device's own readout, you picked the right one.

Limitations

This calculator accepts positive sizes only — entering zero or a negative value shows a “must be positive” message and is not converted. The result depends entirely on the numeral system you select: the same input produces a different MB/GB count in base-10 than in base-2, so make sure the variant matches the device you are comparing against. The tool converts storage capacity only, not data-transfer rates — if you need to move between megabits and gigabits per second, the Mbps to Gbps converter handles rates instead.

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