MB in, GB out, and the honest answer to “1000 or 1024?”
Let’s deal with the messy part first, because every other MB-to-GB tool quietly picks one answer and hides the other. There are two valid conversions, and which one is correct depends on context.
- Decimal (SI): 1 GB = 1000 MB. This is the official standard. It’s what storage manufacturers, network speeds, and phone plans use. The tool defaults to this.
- Binary: 1 GiB = 1024 MiB. This is what your operating system usually means when it shows “GB,” even though the technically correct label is GiB (gibibyte).
So 500 MB is 0.5 GB the decimal way. Type a value, get the result instantly. There’s a toggle to switch to the 1024 basis if that’s what your situation calls for.
Why this confusion exists at all
Computers count in binary, so powers of two (1024) were the natural unit for memory. For decades, “kilobyte” loosely meant 1024 bytes. Then storage and networking adopted the strict SI meaning, where kilo means exactly 1000, and the two definitions collided.
To untangle it, standards bodies created separate binary units: kibibyte (KiB), mebibyte (MiB), gibibyte (GiB). One GiB is 1024 MiB. One GB is 1000 MB. Clean in theory. In practice, Windows still labels gibibytes as “GB,” macOS and most phones use true decimal GB, and almost nobody types “GiB” in casual conversation. So the same “GB” can mean two different sizes depending on who wrote it.
Where it bites you
This isn’t academic. The mismatch shows up constantly:
- Phone storage. A phone sold as “128 GB” gives you 128 billion bytes (decimal). Your photos and apps are measured the same way now, so modern phones mostly stay consistent.
- Hard drives and SSDs. A “1 TB” drive is 1,000,000,000,000 bytes. Windows reports it in GiB but calls them GB, so it shows roughly 931, and people think they were shortchanged. They weren’t. It’s just two unit systems clashing.
- Data plans. Mobile carriers bill in decimal GB. A 10 GB plan means 10,000 MB.
For most everyday conversions (data caps, file sizes, downloads) the decimal 1000 basis is the right call, which is why it’s the default here.
How to use it
Enter a megabyte value and the gigabyte result updates as you type. Leave the toggle on decimal (1000) for storage, plans, and downloads. Flip it to binary (1024) if you’re matching what your OS file manager reports. The reference table lists common sizes both ways so you can see the gap directly. All of it runs in your browser. Nothing you enter is uploaded, and it works offline once loaded.
FAQ
Is 1 GB 1000 MB or 1024 MB?
Both answers exist. The official SI standard is 1000 MB per GB, used by storage makers and carriers. The 1024 figure is technically 1 GiB (gibibyte), which is what operating systems often display while mislabeling it “GB.”
Which one should I use?
For data plans, file sizes, downloads, and drive capacity, use 1000 (decimal). For matching what Windows shows in its file properties, use 1024 (binary). The tool defaults to 1000 since that covers most searches.
Why does my 1 TB drive show as 931 GB?
Your OS is dividing by 1024 three times (binary) and labeling the result “GB,” but the drive maker counted in decimal (1000). The bytes are all there; it’s a labeling mismatch, not missing space.
What’s the difference between MB and MiB?
MB (megabyte) is 1,000,000 bytes. MiB (mebibyte) is 1,048,576 bytes (1024 squared). They differ by about 4.9%, and that gap grows at larger scales like GB versus GiB.
Does this calculate locally?
Yes. It’s browser-side math with both conversion factors built in, so nothing you type leaves your device and it runs without internet after loading.