How many megabytes are in a gigabyte?

Using the SI decimal standard: 1 GB = 1,000 MB. Using the IEC binary standard: 1 GiB (gibibyte) = 1,024 MiB (mebibytes). Storage manufacturers use GB; most operating systems use GiB but label them "GB."

Why does my storage device show a different size in my OS?

The manufacturer rates capacity in SI gigabytes (powers of 1,000). Your OS typically reports in gibibytes (powers of 1,024) while calling them "GB." Since 1 GiB = 1,073,741,824 bytes vs 1 GB = 1,000,000,000 bytes, the same byte count results in a smaller number when expressed in GiB.

What is the difference between MB and MiB?

MB (megabyte) follows the SI decimal system: 1 MB = 1,000 KB = 1,000,000 bytes. MiB (mebibyte) follows the IEC binary system: 1 MiB = 1,024 KiB = 1,048,576 bytes. 1 MiB is about 4.86% larger than 1 MB.

How do I convert gigabytes to megabytes?

Multiply the gigabyte value by 1,000 to get SI megabytes (MB). Multiply gibibytes by 1,024 to get binary mebibytes (MiB). For most practical purposes, multiplying by 1,000 matches what storage hardware advertises.

How accurate is this converter for very large values?

The converter uses JavaScript 64-bit floating-point (IEEE 754 double precision), which handles integers exactly up to 2^53 — about 9 quadrillion. For any practical storage size in gigabytes, the result is exact.

Gigabytes to Megabytes Converter

Name: Gigabytes to Megabytes Converter
Availability: InStock
Author: Nham Vu

Enter a gigabyte value and instantly get megabytes (MB, decimal SI) and mebibytes (MiB, binary IEC), plus a quick-reference table.

Input — Gigabytes

Number of gigabytes

SI vs. binary: 1 GB (gigabyte, decimal) = 1,000 MB. 1 GiB (gibibyte, binary) = 1,024 MiB. Storage specs use GB; your OS reports GiB (but often labels them "GB").

Results

Enter a gigabyte value and click Convert.

Reference Table — Common Gigabyte Counts

Quick lookup for typical file and storage sizes.

Gigabytes (GB)	MB (SI, ×1,000)	MiB (binary, ×1,024)	Typical example

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Summary

Enter a gigabyte value and instantly get megabytes (MB, decimal SI) and mebibytes (MiB, binary IEC), plus a quick-reference table.

How it works

Enter the number of gigabytes in the input field.
The tool multiplies by 1,000 to get decimal megabytes (MB, SI).
It also multiplies by 1,024 to get binary mebibytes (MiB, IEC), treating the input as gibibytes.
Results appear instantly with up to 10 significant digits.
Use the copy buttons to grab any result value.
Scroll down for a reference table of common gigabyte counts in MB and MiB.

Use cases

Check how many megabytes a file size in gigabytes occupies on a storage device.
Understand the difference between advertised storage (GB) and OS-reported sizes (GiB).
Convert RAM or cache sizes from gigabytes to megabytes for detailed reporting.
Translate download or upload sizes into megabytes for quota tracking.
Verify storage estimates when working with cloud pricing billed per GB.
Cross-reference OS-reported sizes (MiB) against hardware specs (MB).

Frequently Asked Questions

Last updated: 2026-07-23 · Reviewed by Nham Vu