How many MB are in 1 GB (SI/decimal)?

In the SI (International System of Units) standard, 1 gigabyte (GB) equals exactly 1,000 megabytes (MB). This is the standard used by storage manufacturers, internet providers, and macOS (since 10.6).

How many MiB are in 1 GiB (binary/IEC)?

In the IEC binary standard, 1 gibibyte (GiB) equals exactly 1,024 mebibytes (MiB). Windows File Explorer uses this standard while displaying "GB", which is why a "500 GB" drive shows as roughly 465 GB in Windows.

Why does my hard drive show less space than advertised?

Drive manufacturers use SI (decimal) gigabytes where 1 GB = 1,000 MB. Windows reports capacity in binary gibibytes (1 GiB = 1,024 MiB) but labels them "GB". The discrepancy grows at larger capacities — a 1 TB drive shows as about 931 GB in Windows.

Which standard does Windows use?

Windows historically uses binary calculations (multiples of 1,024) but displays the label "GB" instead of "GiB". A file shown as 1 GB in Windows Explorer is actually 1 GiB = 1,073,741,824 bytes.

Which standard does macOS use?

Since macOS 10.6 (Snow Leopard), Apple switched to SI decimal units, so 1 GB in Finder equals exactly 1,000,000,000 bytes, matching the drive manufacturer's advertised capacity.

How do I convert MB to GB mentally?

For a quick SI estimate, divide the MB value by 1,000 (move the decimal point three places left). For binary, divide by 1,024, which is roughly the same but about 2.4% smaller. For example, 2,048 MB ÷ 1,000 = 2.048 GB (SI), or 2,048 MB ÷ 1,024 = 2 GiB (binary).

Megabytes to Gigabytes Converter

Enter a value in megabytes to get the gigabyte equivalent in both SI (1000) and binary (1024) standards instantly.

File Size Converter

Megabytes (MB)

Gigabytes (GB) — SI decimal

Enter a value on the left to see results

Common Storage Size Reference

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File / Storage	MB	GB (SI)	GiB (bin)

Summary

Enter a value in megabytes to get the gigabyte equivalent in both SI (1000) and binary (1024) standards instantly.

How it works

Type a value in the Megabytes field to see the result in Gigabytes.
Enter a value directly into the Gigabytes field to convert Gigabytes back to Megabytes, or click the swap button.
Results are shown for both SI (1 GB = 1,000 MB) and binary (1 GiB = 1,024 MiB) standards simultaneously.
Click any row in the reference table to load that size into the converter.
Click "Clear" to reset all fields.

Use cases

Check whether a file or folder fits on a flash drive or memory card.
Compare storage capacities reported by operating systems (binary) vs. drive manufacturers (decimal).
Convert download sizes from MB to GB for data-plan budgeting.
Quickly reference how many megabytes fit in common gigabyte thresholds.
Verify attachment or upload size limits for cloud storage services.
Convert game patch sizes or software installer sizes from MB to GB.
Understand the difference between GB and GiB when benchmarking storage hardware.
Estimate backup sizes when planning cloud or external-drive storage.

Frequently Asked Questions

Last updated: 2026-09-19 · Reviewed by Nham Vu